For more casual use GPS Tracking, I'm using Google Latitude and the API access from Google -- for example I have a tracking application for our next big hike event in October, combined with KML display. This lets our friends and family know where we are on the hike without much effort on my part.
The nice thing about using Latitude is that I can drop it down to cell-tower location and save my battery life for the hike. But this is useless if you're looking for GPS accurate tracklog info (bring an extra battery!)
Google Latitude:
http://m.google.com/latitude
The tracker website I built:
http://torontogeocaching.com/bthike
SkyFire works great for checking if my update went through, as Google Maps displays properly in that browser.