Hi Curious,
It's tricky to sex a rabbit when it's very young. The following is what the book, Rabbits For Dummies by A. Pavia says to do.
1) Gently place your rabbit on his back or your lap. If the rabbitpanics, let him rest a minute and then try it again. If they fuss tomuch, you may want to get the help of a breeder in your area or a vet.
2) Using your thumb and forefinger, spread apart the hair just beneath our rabbit's tail.
3) Push down gently on this area, and the vulva of a female or the penis of a male becomes visible.
There are good sites on this with pictures on the web if you do a search on it.
Good Luck!
-Carolyn