The Biostar A68I-350 Deluxe mini-ITX motherboard is quite decent for the money. The integrated AMD APU can handle roms, old games, indie games, and even some newer games at 720p.
We are going to use this for our nas build. It's not the best option for a nas (I'd rather use it as a media PC for the living room) as it only has three SATA ports, but we really need a new nas. Stay tuned for the freeNAS tutorial.