The catch today is Grammar Ninja.
Grammar Ninja is an educational web gamein which you are a grammar ninja who must find parts of speech by throwing ninja stars at words. Correct answers allow you to continue, while wrong answers literally explode. It's great fun!
Grammar Ninja was created by current USC undergraduate Greg Lieberman for a high school independant study in videogame design.
To create your own sentences download the Grammar Ninja Sentence Creator. There is also a Wii-compatible version.
Grammar Ninja could serve as a very nice interactive whiteboard activity.