I've wanted to build a Mini ITX computer for a long time 'cause it looks like a lot of fun. Dave Glover blogs about the Mini ITX system he built to run Team Foundation Server. If you surf the Mini ITX site, you'll find pics of projects where people have built Mini ITX systems using a wide assortment of containers. See a random Mini ITX project.
I think I'll follow Dave's lead, but I'll build mine inside a Team Foundation Server product box.