I was running Windows 7 on my EeePC and decided to get rid of it. I formatted my drive completely and installed CrunchBang Linux 10 (Statler). Statler is an Alpha release and based off of Debian Squeeze but still running the lightweight Openbox.
For those that are familiar with GNU/Linux know that CrunchBang Linux was using Ubuntu as a base, but now they are using Debian instead. You can have a read about why they switched to Debian.
For anyone with a low-end machine or even wanting to get a nice fast distro running I would highly recommend CrunchBang.