An often asked question is which GPS device to buy and which GPS antenna's to buy. I'm not an expert on either but general wisdom seems to suggest that the Garmin GPS devices are pretty decent and that the "Mighty Mouse 2" GPS antenna is good. One nice thing about the Mighty Mouse 2 is that it comes with a universal antenna connector so it'll attach to pretty much any GPS.
If you are just looking for a cheap GPS to use with only your PC, you can get a Rand Mcnally GPS with their software for about $75. It hooks to the PS/2 port of your computer for power (with an optional lighter adapter) and the serial port.. All it does is spit out NMEA data.. No external antenna connector, and initial acquisition time is pretty bad, but it works pretty good otherwise.
If you have a new laptop that lacks ps2 and serial ports (like my Toshiba), the above comment on Garmin & RM GPS may not work for you. You have a few options:
1. buy the Garmin with the serial cable and then buy a USB to Serial adapter for $20 or so online, only real disadvantage here is that you need batteries or external power source for the GPS plus another for your laptop, advantage is that the GPS functions standalone as well;
2. buy a USB hockey-puck/mouse style GPS receiver (ie Deluo) which will be powered off your USB port;
3. buy a PCMCIA GPS card - not very common;
5. buy a BlueTooth GPS device and a BlueTooth adapter for your laptop/PDA if it does not already have BT, more expensive option because they are newest but arguably you could have multiple BT-enabled devices reading GPS data from it simultaneously;
Personally I chose the GlobalSat BC-307 CompactFlash card purchased from eBay and the external GPS antenna and PCMCIA adapter were both included in my purchase. Negatives to this is that my GPS -ONLY- works with my laptop (or PDA) as there is no screen on the card itself. Price was right around $100 and the performance/compatability of the unit is great, highly recommended.