ArkWords is  a great little app by Arktronic that features not only a great dictionary and thesaurus but an impressive, multi-language translator. In addition, it has a swanky Live Tile that updates every morning with the WOT (word of the day).

The app is superbly built with a very minimalist and fluid UI. Plus it's free, so there's little reason to not give it a shot. And now that the Live Tile has been fixed in v1.1, all seems right with the app and gets our strong recommendation.

Grab it here in the Marketplace and go here for the developer's blog.