Roku's Plex channel is the goods.
I had 3 Mac Minis until today, but was able to eBay the two older ones and replace them with Roku 2 XS's for $199, and pocket $600 from the Macs. Since Roku can pull from Plex Media Server, all I have to do now is turn on my "main" HTPC Mini and either one (or both) can pull from it.
Awesome stuff. Plus, the Roku is tiny - you can double-stick tape it to the back of your TV, and it uses about 1 watt of power.
Everyone should own one of these.
Roku Streaming Players | Roku 2 HD Player, Roku 2 XD Player and Roku 2 XS Player
What can this do that my apple tv doesn't? I don't know these things..