I use these in a couple rooms in my house...
Seagate FreeAgent Theater+
Nothing fancy and the on-screen interface isn't all that great... but the nice thing is that you can either output digital via TOSLINK or over the HDMI. Wireless networking is only supported via dongle, but I just setup powerline networking to the rooms I use it in (bedrooms). Nice for throwing a bunch of DVD/BR rips and a few CDs worth of flacs on a FreeAgent 320GB drive.
Note: You don't have to have a FreeAgent drive in the unit for it to work... you can access network locations on your home network and play shared media from those locations. But if you want to run it without any networking connection - just get a drive and load it up with whatever you want.
I use that for trips if I don't feel like rolling the dice on what the hotel has on the TV... as long as the TV has an HDMI input - I can bring along 100 DVDs on a 500GB drive.
It doesn't handle the uncompressed surround formats for BR-ripped MKVs, however it does do the compressed ones (DTS/DD) and LPCM streaming is supported. In addition to FLAC it also supports most common lossy codecs and a couple other lossless ones I think.
And if you have something against Seagate external drives... or already have everything on a larger USB external... it has two standard USB ports on it too and you can just plug them in and go.
Oh yeah and netflix is nice on it too - although you're limited to just browsing your instant queue... no searching.
This competitive device is much better as far as the interface look and speed... however, I opted for the Seagate because of price + Netflix which at the time the WD unit didn't provide.