I use f.lux and think it's great. I recently started taking a small amount (~1.5mg) of melatonin after reading a post[0] by Gwern and the accompanying discussion on HN[1]. I find that taking it ~30 minutes before I want to go to bed makes it much, much easier to "tear myself away" from the computer, book, etc. and go to bed.

0. http://www.gwern.net/Melatonin 1. https://news.ycombinator.com/item?id=6495358