Spark electronics has a $39 GPS logger that works with Google Earth - "The Lassen iQ FAT16 Datalogger is the latest widget from SFE. This little board will datalog all GPS data (longitude, latitude, speed, altitude, etc) up to 440 hours with a 256MB SD card using FAT16 format! Direct and automatic text file recording! Best of all, you can open the data into Google Earth!" - Link. Matt adds - "$39.99 + about $75 for the extra pieces you need to make it work. That price does not include the GPS receiver, power source and etc.
http://blog.makezine.com/archive/2006/03/39_gps_logger.html