My Airport base station suddenly started dropping signal for a few minutes. The first one I got had issues with the ethernet, but managed to die before the warranty expired.
Attach a USB drive and share it through FTP, NFS or Samba. Nice combination with something like the iaudio.
Attach a webcam (my ov511 based creative cam worked fine, b/w with the default and color with the upgraded firmware. It can even do motion detection and e-mail you a picture of your cat peeing on the keyboard.
USB printer server
Apart from a zillion bridging functions it can also do traffic shaping, yay.
(updated): Oh and they respect the GPL and clearly benefit from the added 3rd party functionality. Way to go Asus Way to go Harald Welte.
The only downside is that you will end up wasting quite some time tweaking the thing. Also it lacks a bit in the aesthetics department compared to the old airbase.