I saw this yesterday over on the Make blog. Adafruit has come out with a new Arduino shield which looks excellent for UAV usage. The shield has support for several gps modules, and can log data to an SD card.
Even with the GPS and SD card, there are still 5 digital and 5 analog IO open.
Here are the details(text below lifted from adafruit.com):
GPS shield for Arduino kit with data-logging capability. After building this easy kit, you can create your own geo-locative project.
This shield is designed to make GPS projects straight-forward and easy. Plug in a supported GPS module and run any of the example Arduino sketches for parsing GPS data (NMEA sentences), logging to a FAT16-formatted SD flash memory card and storing analog sensor data along with precise location, date and time in CSV format.
The shield is designed specifically for use with the EM-406a module: the small surface-mount GPS connector is pre-soldered for you. (It is a high-quality engine with quick time-to-fix and excellent reception, even in downtown New York City!) It can also be used with a Tyco A1035D, EB-85A or Lassen IQ module (see the webpage for more details).
GPS module, Arduino, and SD memory card are not included. Please check the parts list to see what is included. NG arduino users should probably also upgrade to an ATmega168.