the1casey: You first have to ask yourself what you mean by mini-pc and what you want to do with it. There are a few form factors out there. First, ATX is the big one for most standard computers. You can get smaller ATX cases (mini-towers) that will still fit an ATX mobo.
Next, there are the various Shuttle XPCs. The come in one standard case that is cube style. 2 big bays and 2 small bays. http://us.shuttle.com/product_mini.asp
The cases look pretty sweet and come with a motherboard and PSU built in. You must provide the CPU, RAM, Video, HDD, Optical Drives, etc. LAN and not so go audio are built in. Depending on the parts you use, it can be a killer system or just a basic machine.
Finally, my favorite, is the Via Epia platform. Its a 17cm x 17cm motherboard that has a processor embedded in it. You just need the board, case, RAM, HDD, and optical. Only downfall is that is isn't incredibly powerful. It has hardware MPEG2 for DVD, and has enough horsepower to decode DIVX and MP3, but it's definatley not a gaming machine. More of a Firewall/Internet/Email/DVD/MP3 computer for the living room or something similar. www.mini-itx.com
is a good site for info. There are many cube style cases for this. Here's the basic cube for that: http://www.caseoutlet.com/NWPc/Checkercube/checker.html
. There are also a lot of newer cases like this:
on their way. Mini-ITX is exploding, and with the release of the new Epia Ms, there is a lot more power behind the systems than the previous generations.