So I'm heading out to go to NYC tomorrow and I'm trying to connect my GPS to netstumbler. Well, as I quickly found out I was going to need a serial to usb converter. With no time to get it I started googling. 3 hours later I came up with this:
http://franson.com/gpsgate/ It shares and emulates your usb garmin gps to a variety of com ports using NEMA. It is unbelievably easy to use!!! It also works on pocket pc. Hope this helps.