There are now hundreds of thousands of apps available for your iPhone 5, iPhone 4S, iPod touch and iPad, and, surprisingly, many of the best are free.
The following list showcases our pick of the 80 best free iPhone apps, and includes iPhone applications for social networking, travel, news, photography, productivity and more.
Most of these apps are also suitable for the iPod touch.
If your top free iPhone apps aren't covered, tell us all about them in the comments.
You can also take a look through the top 10 free iPhone apps with our nifty video.
The world's biggest social network brings a tightly honed experience to the iPhone and iPod touch, but nonetheless still enables you to access your contacts, feeds and other important information. This sense of focus makes it in many ways superior to using Facebook in a desktop browser.
We did a bit of a double-take on seeing Microsoft's name attached to this, not least given the lack of a price-tag. But PhotoSynth is a really great panorama app; it's user-friendly and fun to use, especially when watching your panoramas take shape while you capture them. (The iOS Camera app also has a panorama mode, but PhotoSynth's more flexible and works with older devices.)
The prospect of Nike+ but better and for free might sound unlikely, but that's what RunKeeper provides. Previously split into 'pro' and 'free' versions, the developer now generously includes all the features in one free app.
That means you can spend no money, yet use your iPhone's GPS capabilities to track your jogging and cycling routes, and examine mapping and details of your pace and calories burned. Activities can be shared online, and treadmill runs and other exercise details can be entered manually.
RSS has a reputation for being a rather dry technology, feeding you dull lists of headlines. Pulse flips RSS on its head, providing streams of feeds that grab your eye with photographs. It's perhaps not for the hardcore RSS crowd, but if you follow a small number of feeds, it's a great choice.
Plenty of apps exist for transferring content between your computer and your device, but Dropbox is free and easier to use than most of its contemporaries. Dump files you want to sync in a folder on your computer and Dropbox for your device will enable you to access them, download them for offline viewing, and, in many cases, view them.
Love Dropbox? Then check out our article Essential tips for every Dropbox user.
6. National Rail Enquiries
For anyone commuting by train, National Rail Enquiries is a handy app to have installed. There's journey planning, timetables and a location-aware 'next train home' option, along with progress tracking, so you can see when a train's likely to show up. It's not as usable nor as pretty as UK Train Times, but it is broadly similar - and five quid cheaper.
FaceTime is a great alternative to standard voice calls, but it's no good if you're trying to contact someone without a Mac or compatible iOS device. Therefore, Skype remains an essential download. The interface is simple and usable, enabling anyone with a Skype account to make free calls to other Skype users and cheap calls to anywhere in the world. If you're on Pay and Go, this is particularly handy, but the app also enables iPod touch users to utilise their devices for calls.
8. Movies by Flixter
Although some aspects of cinema listings app Movies by Flixter are disappointingly US-centric (notably regarding details on upcoming movies and DVDs), it succeeds where it matters. Select a film and the app figures out where you're located, lists nearby cinemas, and displays times your chosen film is showing. Efficiency can be further increased by pinning favourite cinemas to the top of the list.
Virtual pianos and guitars are all very well, but purely digital musical toys are more suited to Apple handhelds. TonePad is the best of them, using a grid-based interface that enables you to turn notes on and off and compose pleasing and harmonious loops; your creations can be edited, saved and uploaded to share with other users.
10. Thomson Reuters News Pro
There are many free news apps, but Reuters News Pro offers a breadth of coverage that makes it a winner. Preferences enable you to tailor the app's output to the UK, and the toolbar provides swift access to news, pictures, videos and stock markets coverage.
The official Twitter app might lack some of the features found in the likes of Tweetbot, but it does provide a sleek and simple means of using the service. It also directly mirrors the latest navigational scheme on the Twitter website.
Check out 10 best iPhone and iPad Twitter apps for alternative Twitter apps we recommend.
In all honesty, Comics is a little awkward compared to using it on an iPad, but you won't find a better comics experience on an iPhone. The app is free, as are dozens of downloadable comics - and once you run out of those, many more are available to buy. Reading works on a frame-by-frame automated 'zoom' basis, and is surprisingly usable.
The Wikipedia website works fine on iPhones, but a dedicated app is a better bet. Wikipanion is a freebie which gives you quick access to article sections, in-article search, viewing options, bookmarking, and the ability to tweet about whatever odd fact you've just unearthed. Also, wonderfully, there are no ads.
Clients to access the popular Evernote service for storing notes and ideas online are available for so many platforms that we half expect a ZX Spectrum app to be announced tomorrow. On the iPhone, Evernote is efficient and usable, enabling you to rapidly scan your notes and also create new ones.
With iBooks on the iPhone, you might wonder why you should bother with Amazon's Kindle. After all, the app's not as pretty as iBooks, nor is there an integrated store (you buy in Safari and sync purchases to the app). However, Kindle offers a massive selection of books compared to Apple's app and the reading experience is great.
16. Around Me
Around Me figures out where you are and lists local stuff - banks, bars, petrol stations and, er, Apple Retail Stores. The app's reliance on Google Maps info means there are gaps, but it's nonetheless handy to have installed when in unfamiliar surroundings, and the 'augmented reality' landscape mode is amusing, if flaky.
17. Dictionary.com - Dictionary & Thesaurus
Over two million definitions, synonyms and antonyms are available in the palm of your hand with this free, offline dictionary and thesaurus. The app is fast and efficient, includes phonetic and audio pronunciation of words, and its interface seems perfectly suited to the iPhone.
18. Air Video Free
Air Video Free can stream (and convert as necessary) video from any computer running the free Air Video Server. You only get access to a small number of items per folder or playlist, but some careful planning can get around that limitation.
19. Adobe Photoshop Express
If you're looking for Photoshop-style power, Photoshop Express won't impress. However, if you're after a quick, free, highly usable tool for making edits to your iPhone photos, Adobe's app is ideal. Use it for cropping, straightening, exposure adjustments, colour effects, sharpening and more.
For more cool iPhone image editors, check out 10 best iPhone and iPad photo editing apps.
20. iHandy Level Free
One of the tools from the excellent iHandy Carpenter toolkit app, iHandy Level Free turns your iPhone into a spirit level. By default, it'll show just how wonky your device's accelerometer is, but tap the calibrate button and you get an accurate and great-looking level.
Before reading on, why not check out TechRadar's top 10 ebook reader apps for iPhone:
The service formerly known as Read It Later enables you to save pages from websites, to read them later, bereft of the advertising and other junk on the original page. The service is free, as is the Pocket app, which downloads your articles, so that you can digest them without a web connection.
22. PCalc Lite
"But I've already got a calculator on my device," you might argue. True, but we'd recommend stashing the default Apple app in a folder and replacing it with PCalc Lite. The reason: this is without doubt the finest free calculator for iOS, with a great interface and plenty of options. You can also bolt-on features from the paid version via in-app purchases.
Effectively iTunes for books, the app combines a reader and store, in Apple's typically usable and integrated fashion. Usefully, iBooks includes PDF support and bookmarks automatically sync across devices.
24. RL Classic
The RL Classic bar-code scanner is pretty accurate, even if you're still saddled with an iPhone 3G. It's great for checking prices while shopping, and also enables you to get your media collections into Delicious Library if you make use of AppleScript.
On using the eBay app, there's a good chance you won't go near the eBay website again. The app is fast, has great saved searches (which flag new finds), and enables you to create listings. The last of those things is also improved by the built-in bar-code scanning.
Before reading on, why not check out our demos of the best photography apps for taking pictures and editing them on your iPhone:
26. Tube Map London
At its most basic, Tube Map London is a London Tube map on your device, for free. In landscape, even the ads get out of your way, which is rather nice. And if you've a web connection, the app also provides live board info, a station finder and a route calculator.
27. Google Earth
"Hold the world in the palm of your hand," says Google about Google Earth, which enables you to fly across the planet by swiping your finger. More integration with content and features from Maps would be good, but Google Earth's Wikipedia articles and a Panoramio layer at least ensure it's a great app for seeing the world from your living room.
28. XE Currency
XE Currency is a fine example of an app that does what it needs to, without fuss. You configure a list of currencies, and it shows current conversion rates. Double-tap a currency to set its base rate or to define values for custom conversions.
Shazam is an app that feels like magic when you first use it. It's deceptively simple—hold your iPhone near to a music source, and wait while the app listens and tells you what track is playing. But the sheer technology behind this simplicity is mind-boggling, and while Shazam doesn't always guess right, it's worth a download.
Another contender for the 'surely, that's witchcraft?' award, Bump enables you to select up to four contacts, then 'bump' your device into another iOS device running Bump to transfer details, or to compare contacts. And, yeah, we know there's an email-based 'share contact' option in Contacts, but where's the fun in that?