How Close is the Open Entertainment Center?

why-not-now asks: "Recently there's been a lot of talk about open source/free software that enables your PC to act as a DVR, all-purpose media player, DVD player, CD player, MP3 player, etc... not to mention the ability to play all sorts of video games (if you know where to look). The idea of the set top MAME console is nice, but with a little TV/Audio out, a little know how and the right software, are we currently able to put together a free version of the big convergence media center others are trying to do?"