I think there are a fair amount of 5 letter domains out there yet. (here are the few 5-6 I've registered: kleevr.com, kratr.com, rabyt.com, exphi.com, excyt.com, xcytr.com, zroone.com, onezro.com, grabyt.com)

Whether these qualify as 'good domains' might be in the eye of the beholder, but I like them and have pretty good ideas sketched up for most of them.