I should note, there's plenty close to home if you want to get out on the roads and crank out a few fast miles. (Since I'm typing this on Saturday AM, I'm going to skip to the Sunday races, but if you're reading this right now, click thru and scroll down to see what you can do at the last minute.)
Close to home, there's a biathlon in Prospect Park on Sunday called the Brooklyn Bun. Ride 20K, race 5K (and they've got a pretty cool logo, that I've hopefully embedded correctly above.). There's also the Bronx Biathlon in Orchard Park.
*Head up to Queens and run the Alley Pond 5-Mile on Sunday
*City Park Foundation 4 Mile Race in Central Park (NYRR) still has spots open on Sunday, and there are kids races there as well.