Holy geography geek, Batgirl! Google's released Google Earth, a downloadable 3D mapping application that starts you out looking at a view of the entire planet, and lets you fly all over Earth to locations you specify, search, add bookmarks and annotations to places and get directions.
Save your searches, overlay images onto maps, save maps as images, see the lattitude, longitude, elevation and display location indicators of ATMs, gas stations, grocery stores and pharmacies. Google Earth is simply awesome; the only unawesome part are the somewhat limiting system requirements: Windows 2000 and up only (Mac coming soon), a Pentium III or better, at least 128 MB of RAM, and certain video cards. (In other words, a fast, relatively new computer.) Free download.
Google Earth [Google via Google Blogoscoped]
Update: A reader reports Google Earth requires a login to use after it's downloaded and installed, but that didn't happen for me. Anyone else run into this problem? Lemme know - tips at lifehacker.com. Update update: That's all resolved. Carry on.