Freenas is cool, but for many reasons I'd rather go with debian. Too bad there isn't a debian distribution designed for compact flash installs (low writes, temp logging, readonly mounts, etc).
What really want:
Is this possible? Should be! Hmmm, just noticed that the Linksys NSLU2 price has been reduced at Amazon.com, its now only $75 and comes with free shipping. Check out the details at mytechdeals.blogspot.com.
Here's some links I found related to the subject of installing Debian on CF: