At first glance the Sans Digital's MN2L NAS looks pretty standard. It has two SATA drive bays, USB2, Ethernet, and even FTP access. But what sets this NAS apart is the built in iTunes support. It can take your music files and dupe iTunes into thinking that it's just another PC and then streams the audio files to any PC/Mac running iTunes. This looks to be a great alternative running a separate PC as a dedicated server. The MN2L is available now and will set you back $299. [Product Page via Electronista]
AU: I have an Infrant ReadyNAS NV+ that also does iTunes support.