I first heard about the Pomodoro Technique by @sugarenia. The technique is basically this:
Work on a task for 25 minutes (a “pomodoro”) and then take a break for 5 minutes. Every four pomodoros, take a longer break.
Like the book proposes, I am using a kitchen timer (I did so after reading Lakein’s book back in 2008). Besides using hardware, there exist a number of software packages that countdown from 25 minutes. I think however, that that following shell script is among the simplest (if not the simplest) implementations:
#!/bin/sh ( sleep 1500 && xlock ) &
If you find the xlock(1) approach harsh, you can always use a variation like xsetroot -solid red.
( Tested on OpenBSD-4.7 )
Managing organized complexity 
http://cd.justinjc.com/25
Does the pomodoro technique (per se) work or partially work for you?
It sometimes does. Especially if I have a lot to do and do not want to context-switch all the time. That way, it allows me to handle interruptions, since I can deal with them after 25 minutes (max).