Tom's Hardware has reviews of two of the new bare bones systems from Shuttle.

Read the reviews, Tom says it better than I can.

One of my auxiliary machines is a shuttle, and they're a great design. They're nice and clean to work on the inside of, and more than quiet enough to have on your desk (not like my BigBlackMonolith file server - if I had another room to put it in, it would be there - way too many fans in there, and boy is it loud). Unless I need a lot of drives in a machine, I reckon shuttle is the way to go, every time. The two reviewed models also have PCI Express on board, instead of AGP. Nice to see someone advancing these new formats - it's the only way they get better market penetration.