Raspberry Pi, the tiny, ultra-cheap, Linux-based PC, went on sale Monday in the U.S. through retailer Allied Electronics, but it's already out of stock. The A version of the computer, which only costs $25, has 256MB of RAM, a single USB 2.0 socket, an HDMI, SD card, and 3.5 audio sockets, but no Ethernet port. Available only through Allied, the A is now completely out of stock for U.S. customers. The $35 Raspberry Pi B is also out of stock at Allied, but it can be bought through Newark, another retailer, which only carries that particular model.