This doesn't seem to be working for me with Firefox 3.0.1 and the latest version of Greasemonkey. Anybody have any ideas why? All I did was add websites using the "add" button under the GM preferences.

This is excellent, and very helpful.

One suggestion I'd like to make (I don't know how to code it or I would, sorry): is there any way to implement a "snooze bar" that you could use once that would give you an additional, configurable, amount of time before starting the block period?

I find the transition is too abrupt when I access a page and all of a sudden the block is on -- it tempts me to turn the script off, and that's not good.

I made a slight modification that I think should be included in the script. I like to be prompted when I can finally visit a website. To do that, after this line:

alert("You have "+mins+" more minutes until your next surfing break.");

add this:

setTimeout("alert('You may now browse freely for '+surf_for+' minutes.');",mins*60000);