Mine has a usb port. When plugged in, it mounts up on the desktop like a flash drive, with all the data folders freely available for reading. I can even drop stuff onto it as a normal flash drive, but the gps itself would have no use for that. But I did for example, drop a copy of the complete owners manual in pdf form on it, perfect place for it.
Serial port eh? So you are stuck with NMEA support. I wrote a plugin for that many years ago. It's not a bad format. Try to find software that supports it. You won't have support for many of the newer gps features like waypoints and trackback logs unfortunately. The main use for NMEA was to allow a computer or other device to obtain current information from the device, such as location, elevation, speed, course, satelite count and strength, etc.
I used it to hook to my powerbook g3 where I had downloaded satellite imagery for the area, and with my GPS3+ feeding position information to it, my app drove a red dot around on the overhead view, james-bond style from the 60's. Rad at the time...
