Bought me a Dlink DNS 323 nas box the other day. Has a gig ethernet, web interface, FTP server, DDNS client, Bittorrent client, and holds 2 x 3.5 sata drives.
Its Very small.. about the size of 1/2 loaf of bread, requires NO tools to install the drives.
Does not seem to allow AD permissions but for adding a storage device to your lan its VERY nice..
It also has a USB print server in it tool.