TOPIC: Google MashUp - World66.com
Google MashUps are, in my opinion, some of the coolest (though oft times useless) apps on the Internet these days. I've had a lot of fun perusing the websites dedicated to mash-ups. Since I'm on a 10-day trip to New England, a relatively new mash-up caught my eye. It's called World66.com. The site allows you to map all the states, countries and continents you've visited. It also offers lots of travel info and advice. The downside (IMO) is the site also has advertisements and commercial related pages. Overall, World66.com is a cool mash-up based on Google Earth technology.
In case you're wondering (and even if you're not), here's a map of all the US states I have visited or lived in:

create your own personalized map of the USA
or write about it on the open travel guide