If you're interested in running networking applications on small hardware, you may be interested in the Beaglebone. It's more expensive, but vastly outperforms the Pi with regards to network I/O. The Pi is awesome for video, however.

It's ENTIRELY possible that that I didn't tune it correctly, but when I was looking at it as a routing underlayer for Tavern.com, it didn't leave me a whole lot of resources for running my apps.