The Raspberry Pi Compute Module is Raspberry Pi's new product specifically designed for makers who want to develop and build their own PCBs. It has most of the power of a Raspberry Pi B+ without some of the bells and whistles. This gives it a much smaller footprint (68mm x 30mm), allowing you to build off of your Pi without having to carry around your credit card sized computer.
The compute module has a BCM2835 chip with 512MB RAM and 4GB eMMC flash memory - which is the equivalent of a SD card in your Raspberry Pi. The board fits into a DDR2 SODIMM connect - which is used for your laptop's memory. This doesn't mean you can stick the compute module into your laptop but it does mean setting up the compute within a custom system should be relatively easy.
Dimensions: 68mm x 30mm x 1mm / 2.7" x 1.2" x 0.04"