There’s currently an alternate reality game going on around the NBC show Heroes called Heroes 360. One of the characters from the show, Hiro Nakamura, has a blog that often features puzzles and clues for the game. One of the most recent puzzles is a crossword puzzle that’s quite challenging.
Btw, the popular blog for tracking the Heroes 360 can be found here:
http://heroes360clues.blogspot.com
Their updates are great, and there is a good community connected to it.