[ndcrandall]

I agree with these suggestions, and I'd like to add to #1.

Get away from your usual place of work. If you can go to a place such as a library, empty office space, or school campus you'll be more focused. These places should be a bit unfamiliar so you're not as comfortable there. Don't think this applies to everyone, but I have seen it work well in my situation.

I have to admit I sometimes find myself in the same boat as this post and I'm always looking for ways to improve productivity.

[GeneralMaximus]

This works very well for me. Sometimes, just moving away from my main work area to another room works wonders for productivity. Heck, changing my Emacs color scheme sometimes makes me feel more inclined to work. It's not a replacement for true discipline but it's a neat trick that can get you out of a rut.

Humans crave novelty, some more than others.

[Tangaroa]

This worked for me. When I needed to get work done on a school project, I would get off my home computer and head to the school labs or go in to work after hours. I was far more productive than staying at home.