Gmail, Twitter, Facebook, Flickr - a few giants so dominate the web app world that it's hard for anyone else to make an impression.

We've spent some time looking beyond the leading sites, though, and discovered a host of interesting tech startups.

Some take existing web app ideas and add a new spin of their own. Others are more innovative, using fresh concepts to deliver powerful new ways of using the web. But they're all worthy of your attention - and here are 20 of the best.

1. TeamLab

Big business has long understood the value of powerful and efficient collaboration tools - and now TeamLab is making them available to everyone. Project management with tasks and milestones; instant messaging via a built-in web client; blogs, forums, news, polls, photo albums, a wiki and more, are all yours for free.

TeamLab

The service is perfect for small businesses, clubs, or any group of people who need to work together online. And the platform is open source, too, so you can alternatively host TeamLab yourself or extend it in any way that suits your needs.

2. Roc

Roc is a free online music creator that's entirely browser-based, point and click - no musical ability required. It looks like most other loop creators, in that you choose from a decent selection of instruments (there are 10 drum types alone), assign them to tracks and then click to create notes.

Roc

Editing options are unsurprisingly on the basic side, but Roc is a lot of fun to use, offers plenty of scope for creativity and lets you save the results as an MP3 file when you're done. (The instruments are all Creative Commons-licenced, too, so whatever you create can be used in any way you like, no royalty restrictions to worry about.)

3. BuzzVoice

Time. There's really never quite enough, is there? But maybe BuzzVoice can help. This clever app grabs news from your choice of more than 1,600 top blogs and news sources, and converts them into audio files in real time. You can then stream the audio directly to your PC, listen to it on the go via the BuzzVoice iPhone or iPod touch app, or save it to your MP3 player for playback any time.

BuzzVoice

The free version of buzzVoice has ads and some limitations - you're allowed a maximum of 10 web sources in your personal playlist, for instance - but it worked for us. And if you need more, then the commercial BuzzVoice Pro can be yours for $3.99 monthly.

4. HomePipe

Music, videos, pictures, work documents - your PC is packed with important files. And now, with HomePipe, you can access them from anywhere. Securely share the folders you need, then access your content via an iPhone or iPod Touch, Android mobiles or other PCs. The system is currently a little basic, but it's easy to set up, and allows you to, say, stream all the music on your PC to your phone.

HomePipe

5. Resnooze

Resnooze is a well-designed reminder application that makes it easy to be prompted for recurring tasks (daily, weekly, monthly and so on). Just enter a line of text about whatever it is you need to do, choose the task frequency, optionally share the alert on Facebook, and that's it: you'll now be sent regular reminders by email, so you'll be able to access them from anywhere.

Resnooze

6. Scrumy

Organising a group of people to work on a project can be complex, difficult, time-consuming - or you can just use Scrumy. There's no registration involved, just enter a project name and you're off.

Next, enter some "stories", high-level goals that you'd like to achieve. Then create a few to-do lists that will help you get there, and assign individual tasks to your friends and colleagues. They can then log on to see what's required, change the status of various tasks - set the first to "In Progress", say - and keep an eye on what's going on.

Scrumy

Scrumy is basic, but also simple to use and very effective. You have to be careful about what you put on your page, though - it's public and can be viewed by anyone who enters your URL. If that's a problem, check out Scrumy Pro, which adds password protection and a number of other useful extras for $7 a month.

7. Good Noows

Good Noows is a stylish feed reader that collects the news from your choice of topics and sources, then assembles it into an eye-catching newspaper-type layout. The app is particularly strong on visual styles - every topic can have its own look, if you like. And if you spot a story of particular interest then you can share it on Twitter, Facebook, MySpace and more in a couple of clicks.

Good noows

8. Touration

If your website is complex, then it's important to give your visitors the guidance they'll need - and Touration makes this very simple. The site allows you to build guided tours for your site, with multiple callouts explaining everything the viewer needs to know. This is all done within a simple WYSIWYG editor, so no need to write code or worry about scripting issues.

Touration

You will have to embed a simple script into your web page to make this work, but the Touration site has plenty of guidance on how to do this so it shouldn't get in your way.

9. iSendr

When you need to send a huge file to a friend then there are plenty of services that will host it for you. But what if it's something confidential, private, a file that you'd really rather not leave on some distant server? Then iSendr could be a better choice.

iSendr

Point the program at the file on your PC, give your friend the private link, and they'll be able to download it - but directly from your system. The connection is encrypted and the link can even be password-protected for additional security.

10. Online Converter

There are plenty of sites around that perform some useful file conversion, such as transforming HTML code into a PDF document. Online Converter goes a little further, though, by providing tools to transform audio, video and image files, documents and eBooks from one format into another.

Online converter

There's excellent format support, so for instance the site can handle 11 image file types, and 9 eBook variants. And the Video module is able to output movies targeted at particular devices, including the iPhone, iPod, Nintendo DS, PS3, PSP, Wii, and XBOX360.