In case you're not spending enough of your time playing word games, solving riddles, and generally frittering away your day while exercising your brain... have you checked out Word Sudoku yet?
I did a search tonight, and came across a few sites. This seemed the most promising, not to mention it was the least likely to make me want to commit Sudokicide.
This one is a little more confusing, but the site itself has other good puzzles. Like Cryptograms. Or Acrostics. But not Word Ferret. Don't check out Word Ferret because we might never see you again.
And then this odd variation of Sudoku is like a Sudoku crossword puzzle. It's called Kakuro. Brave? Try it!