While reading this article, I realized that somewhere around half-way through I had switched to another window to send an IM about something that had popped into my mind. It was a bit ironic.

I used to do work in 20-minute sprints. It was originally for eye strain, but I found myself very productive for those 20 minutes, as if I was driven to be sure I got things done such that the break didn't severely interrupt me. It really helped me focus on results.