The Pomodoro technique has gained a lot of attention in recent years. It's incredibly simple, requires virtually nothing to get started, and it fits in well with just about any organisational system.
As its popularity has increased, so have the number of Pomodoro apps available - which is where the Pomodoro Apps Guide comes in. I've tried to cover the main categories (online, desktop and mobile) as well as give a little rundown about the app.
The full guide can be viewed here: Pomodoro Apps - it's still very much a work in progress, so I'll be adding new apps as I go.