The Raspberry Pi Model A is the $25 computer the Raspberry Pi Foundation promised. It is the low-cost, low power little brother of the Model B boasting the same processor and high resolution HDMI output. The Model in contrast to the Model B uses only 1-2 watts of power compared to the 3-5 watts of the Model B. This makes it great for use in mobile applications where power is very limited. A perfect application for this would be a wireless media center streaming media over the network.
Here is a run down of how the Model A and B compare: