DDR has never been better. Introducing Dance Dance Immolation! Hit those dance moves well and and you get big propane blasts up in the air. Dance poorly and it shoots fire in your face instead.
Google maps and earth are pretty cool themselves, but it seems everyday someone is coming up with a cool new use for them. Tripods is a multiplayer Google maps game. No, it's not “quick, who can find the latitude and longitude of the Eiffel Tower?” It involves blowing up tripods invading Manhattan - and really, what more do you want in a multiplayer game?
I found both of these by perusing the social bookmarking site del.icio.us. Check it out if you haven't already. The tagging system might be new to you, but once you try it out for a bit you'll forget bland hierarchical categorizing. You can subscribe to other peoples' links or specific tags of interest (ergo the “social” nature). RSS feeds are available for the geeks.
Here's my.del.icio.us; let me know your username if you're on there.