Early last year I had the opportunity to check out the NAS 2.0 adapter from Addonics. This was an excellent little gigabit USB NAS adapter that you could purchase for under $70. For that price you got an outstanding little all-in-one NAS unit - it supported printer sharing, USB drive sharing, samba/FTP/uPNP access, as well as highly customizable network settings and even a built-in bit-torrent client. The NAS 2.0 seemed too good to be true for the price - but it wasn't, and despite lacking a little in the GUI department, it performed quite well in my tests.
Now, a year later, Addonics has improved on the NAS 2.0 and released the NAS 3.0. Great news - it's only $5 more than the NAS 2.0 and still one of, if not the most, affordable USB NAS device on the market. Addonics has made a few great improvements on the NAS 3.0 - there's support for drive volumes over 256TB in size, a much improved web GUI, and WebDAV support to easily create your own cloud at home.