Check out the Lassen iQ FAT16 Datalogger. its a kit you buy that comes with the GPS antenna, data logger, SD Card, batteries, etc, and you build a complete working GPS data logger. comes with a 256mb card, and it can record either NMEA raw data or Google Earth KML files. in KML format you can get about 440 hours of recordings. not bad, but now much in NMEA mode?
i will be getting me one of these, mainly for geek reasons (i already have a Bluetooth GPS device, and a USB one for the computer). but it will be handy for photography. using a tool like RoboGEO i can tag all my photos with GPS info. Very handy!