I use a variation on pg's laptop-across-the-room-plus-no internet-on-dev-machine trick.

I need internet for what I do, but I keep all of my bookmarks (especially RSS feeds) on my laptop in the next room. The laptop is also at bar height, with only a hard plastic stool in front of it. So procrastinating for too long is uncomfortable.

I can still go to various distracting sites (I'm doing it now), but it's a decent speedbump (and noprocrast is your friend).