Ask HN: What do you do while compiling?

My project takes a long time to build: 15 minutes for a clean build, 5 minutes for a minor change. At some point in the day, I've caught up with the interesting articles on HN and Google Reader, and then I struggle to find more interesting things to read. I feel like I could make better use of the time, but trying to learn a new language or start a project in 5-minute bursts doesn't work too well for me.

What do you do?