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$30 GPS Core

Radio Shack is closing out some of its DigiTraveler GPS core devices for a ridiculously low price of $30. They're serial peripherals for computers and PDAs, not stand-alone devices, but if you have any interest in geo-hacking, you can't beat the price. They're hockey-puck-sized devices that are powered by 3xAAA or a 6V adaptor, and they spit out standard NMEA serial GPS messages at 4800 bps. There are two models: the 20-1601, which comes with software and cabling for iPAQ 3670/3685 & Palm m125/m130/m500/m505/m515/i705, and the 20-1602, which has a standard DB-9 serial cable and Windows software (the GPS unit is the same for both models). Unfortunately, I couldn't find a single 1602 unit in the Boston area, but the 1601s were easier to track down (I know for a fact that there are still a couple at the Meadow Glen Mall Radio Shack.) Given how freakin' many Radio Shack stores there are, you're bound to find a few units in your area if you act quickly. If you can only find the PDA version, you can get a PC cable shipped to you for $18, or you can roll your own using standard serial and phone connectors.

More technical details on the device here, here, and here.