Hack your to-do list!
This iPhone app is a timer for Merlin Mann's Procrastination Hack, aka "(10+2)x5".
The idea is that you commit to working on a task for 10 minutes, not necessarily completing it, but getting it closer to being done.
When the timer ends after 10 minutes, you have exactly 2 minutes for a break to do whatever you want - read email, surf Reddit, whatever.
Repeat 5 times to hack your procrastination into oblivion!