We've previously suggested that social check-in service Foursquare can be more than just annoyingly self-involved, including its use as a self-tracker. Turns out it's seriously simple to track your wanderings, for expense sheets or other means, with Google Maps.
Foursquare offers a nice selection of feeds to its users, including a map-friendly KML link. With that, it's dead simple to make an instant map of everywhere you've been recently:
Beyond tracking your travels for personal reference, having those points on a Google Map allows you to "star" them for later ease of finding, as well as dig up information like phone numbers and easy distance calculations for tracking your exercise. Neat stuff.
Display your foursquare checkins on Google Maps the easy way [About Foursquare via A VC]