17. Friend Stats
Though not the most useful application on Facebook, Friend Stats is certainly one of the most interesting. Combining natural nosiness with mathematical wizardry, this application mines your Friends List for data then presents the results in bar chart format. Find what your films your friends, their average ages and political affiliations. There's even a bit of numerological data to be gleaned from your mate's names. Maybe you'll learn something about yourself...
18. Facebook Marketplace
Facebook's Marketplace is no substitute for a dedicated auction sites like eBay, but it is handy for local classifieds. Like other free ad services, Craig's List comes to mind, you have to wade through some spam to find the genuine offers. To make browsing easier, the classifieds are divided into categories - and you can add your own listings, too. Marketplace is added to your Facebook profile by default.
19. Facebook Mobile
Catering for Generation TXT, Facebook Mobile is exactly as it sounds. O2 users in the UK can upload photos, poke people and post wall messages using text messages sent from their mobile phones. Yes, the app version is restricted to one UK service - but any web enabled phone can access Facebook via the mobile site - m.facebook.com . T-Mobile users should be aware - you may need to alter your security settings.
20. Texas Hold 'em Poker
There are a few poker applications on Facebook, but with five and half million users Texas Hold 'em Poker is the ace in the pack. It's slick looking and colourful, with easy to follow prompts onscreen. You can play for free, with tokens instead of real cash, against other Facebook users. Your identity's safe unless you choose to reveal your name, so feel free to hone your gambling skills without splashing any cash before you hit the real casinos.
Now read the top 15 things you should never do on Facebook