I've used Yesod for a small webapp. The type-safety is amazing. For a simpler project, I've used a small subset of Snap. Well, the HTTP side was simpler: it wa

I've used Yesod for a small webapp. The type-safety is amazing. For a simpler project, I've used a small subset of Snap. Well, the HTTP side was simpler: it was a game with the front-end completely in JS, and the server in Haskell; all Snap did was shunt JSON back and forth through a few routes for creating a new game, getting the updated game state, posting a move, etc. Both are nice, depending on what you need, but for your average Django or RoR developer, Yesod gives the most bang for the buck in terms of learning a completely different paradigm.