The typical computer system that an enthusiast would use for gaming or general office work uses an ATX form factor mainboard. There are some cases where the ATX form factor is too big, like SFF computers and HTPC machines.
Some pics of a new Gigabyte mainboard for compact computers using the mini-ITX form factor have surfaced. The new board is called the H55N-USB3 and as you can gather by the name of the board, it sports USB 3.0 connectivity. CPU support for the board is for Intel LGA1156 processors.