So while browsing on Flickr, I came across a link to Douwe Osinga's Visited States. It's pretty simple: you click on the name of the state you've visited, and the state gets marked in red on the map. I've visited half the states in the Union:

create your own visited states map or check out these Google Hacks.

I have some personal criteria for what constitutes a "visit". For instance, I didn't count the layover in Salt Lake City as a visit to Utah. I don't think you can really call it a visit when you never leave the airport. Likewise, I didn't count the short time I spent in Newark, leaving from the airport to go in to Manhattan, as a visit to Jersey. I don't count the approximately two hours I spent at a friend's father-in-law's place in Oklahoma as a visit; we were there to pick up dad-in-law's old big-screen television, and it was right back across the border in to Texas. However, though we didn't spend a night in Maine, or Vermont, I count those as states visited, since we were there to see certain sites unique to the state, i.e., playing tourist. So you may feel otherwise as to what makes a "visit", but that's some of what I thought about when marking states. So how many have you visited?