The highly anticipated Sony PSP GPS receiver accessory started to ship in Japan last week. Japanese gaming gear exporter Play-Asia is taking orders for it, but states a 1-2 week shipping time-frame.
Sony officially announced the Sony PSP-290 GPS accessory in September in Japan only. There is no word yet, when the GPS receiver will be released outside of Japan.
You can order the PSP GPS receiver for $59.90. Price in Japan for instance on Amazon.jp is ~$48. The Maplus navigation software with the GPS support is going to be available December 14th and also games like Metal Gear Solid and a Golf game are supposed to support the GPS receiver.