If you're not reading Lifehacker, you should be.
I've been looking for a Raspberry Pi project to try out, and I may have found one. If you're not familiar with Raspberry Pi, it's one of the coolest things out there for DIY projects. It's basically a single-board Linux PC, the size of a credit card, and it goes for $25 ($35 for the version with more RAM, 2 USB ports and a LAN port). Read up on it and check out Lifehacker for project ideas.
A couple years back, Mrs. Tunnel and I were talking about building a MAME cabinet from scratch. It turned out to be more time and money than we wanted to invest. This epic slice of awesome is a pretty simple build (I've got an unused monitor and VESA wall mount bracket already) and it's inexpensive. I think I'll be putting in an order for a Raspberry Pi this weekend. Updates and pics to come as the project progresses.