Fancy fixing your ebook collection, transferring DVDs to your tablet, resizing hundreds of images or just cleaning and speeding up your computer?

These tools can do all of that and more – but their best feature may well be their price tag, which is zero.

The following programs prove that sometimes, the best things in life really are free – and that's why they're at the top of our must-have list whenever we get a new machine.

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AppCleaner (Mac)

Download AppCleaner (Mac)

AppCleaner

AppCleaner is a simple program that does one thing very well: it keeps an eye on the applications you install on your Mac and gets rid of them properly if you decide you don't want them any more. That's handy, because removing applications the standard way doesn't always get rid of associated files and plug-ins.

AppCleaner is particularly useful on MacBooks with their often limited solid-state storage. Looking for a Windows equivalent? We thoroughly recommend the excellent Revo Uninstaller.

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Audacity (Windows, Mac, Linux)

Download Audacity (Windows, Mac, Linux)

Audacity

Audacity is a sound studio, and while it isn't the prettiest app, it trims, de-noises, converts, speeds up, slows down and adds effects to audio files beautifully.

It's particularly useful for audiophiles, as it supports lossless FLAC files as well as the usual WAV, AIFF, MP3 and Ogg Vorbis formats. It can even rip music from cassettes, detecting track gaps and splitting the sound files accordingly. Cassettes!

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Calibre (Windows, Mac, Linux)

Download Calibre (Windows, Mac, Linux)

Calibre

Calibre is the Swiss Army Knife of ebooks: it effortlessly converts ebooks from one format to another, enabling you to switch hardwares without losing your library.

It has a built-in web server for accessing your ebooks from anywhere on Earth, and its editor supports the major ebook formats and can fix the most common formatting errors. It's particularly good for large content libraries.

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TuneUp Utilities 2014 (Windows)

Download TuneUp Utilities 2014 (Windows)

TuneUp

AVG's TuneUp toolkit is designed to take the hassle out of optimising Windows, and its 15-day free period is more than enough time to spring clean even the unhappiest PC. It can clean up Windows 8.1 apps, find and remove duplicate files, clean up your hard disk, streamline startup options… if it's tweakable, TuneUp can tweak it.

It can even make your PC prettier: if you're running XP, Vista or Windows 7 you can customise the user interface.

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Firefox (Windows, Mac, Linux)

Download Firefox (Windows, Mac, Linux)

Firefox

Firefox isn't just here because it's a great browser. It's here because extensions make it great at pretty much everything. Want to block images and ads, download videos, edit websites or discover how trustworthy the site you're visiting really is?

If you can imagine doing it online, there's bound to be a Firefox extension for it.

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GIMP (Windows, Mac, Linux)

Download GIMP (Windows, Mac, Linux)

GIMP

The GNU Image Manipulation Program has come a long way in a relatively short time, and the current release manages the trick of being advanced enough for pro users yet simple enough for relative newcomers to image editing.

It's the most powerful free photo editor around, and while it takes a while to learn, it's an investment you won't regret making.

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Handbrake (Windows, Mac, Linux)

Download Handbrake (Windows, Mac, Linux)

Handbrake

We're big fans of Handbrake, the excellent open source video converter: it'll happily back-up DVDs to the format of your choice and convert media files, Blu-Ray and DVD sources to make them work on your chosen mobile device or media streamer.

Plus its selection of presets – from Apple's iPod to Android tablets – makes the process as simple as possible. Naturally there are detailed options for advanced users too.

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Irfanview (Windows)

Download Irfanview (Windows)

We've been using this one since PCs were made of wood. Don't let the ancient-looking website fool you: Irfanview remains one of the most useful image tools around thanks to a combination of simplicity, speed and batch processing.

It can convert almost any image format to almost any other, resizing and resampling as it goes. It's brilliant.

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LibreOffice (Windows, Mac, Linux)

Download LibreOffice (Windows, Mac, Linux)

LibreOffice

Need an Office suite but don't want or can't afford Microsoft Office? LibreOffice is as good as its tagline ("Free Office Suite - Fun Project - Fantastic People") suggests.

It's a free, open source alternative to Microsoft's suite, it plays nicely with Windows 8 and it's updated more frequently than Apache OpenOffice. It isn't quite as powerful as Microsoft's offering, but it's an awful lot cheaper.

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VLC (Windows, Mac, Linux)

Download VLC (Windows, Mac, Linux)

VLC

VLC is a media player that can play pretty much anything – and it can do it without having to download a whole bunch of codec packs for audio and video.

Ad-free, spyware-free and completely free, it can play media web streams, damaged media files and even files that haven't finished downloading. If you're considering a music or video player, try this one first.