You might have heard of Apple’s Time Capsule (an 802.11n router-n-NAS) which will make backups simple for the first time if and only if you run Mac OS X Leopard. Anyway, for those that already had non-HPFS NAS solutions, this is what you can do to make them work with Time Machine:

sudo defaults write com.apple.systempreferences TMShowUnsupportedNetworkVolumes 1

Nice, huh?