Rated 4 out of 5 stars
I love LeechBlock. When I take breaks from paper-writing I tend to spend way too long distracting myself with social networking or recipe sites. I have it set to allow me 10 minutes of distraction every third hour from 8:00 to 6:00, which are my usual studying hours. This is AWESOME for keeping me on task.
A great feature would be a reverse-block list, where you set up a list of sites you can access during the blocked time and block all others.
Thanks for the review. Actually, you can set up a reverse-block list already, using the wildcard (*) and exception (+) features. See the examples page for details.