CrossTips gives you quick hints whenever you’re stuck at a particularly difficult Crossword puzzle.

crosstips

You can search for all words by word length, and by specifying various letters in the word. Crosstips supports both US and British English, as well as Swedish.

If you feel this is too close to cheating, here’s some good rationalization from the creator, “It’s not cheating if you really got stuck simply don’t know the word you’re looking for”.