GHC 7 can use LLVM as a backend. That might allow generation of JavaScript code from Haskell. There's already ghcjs (https://github.com/sviperll/ghcjs), but the output from that is quite verbose from what I've seen so far.

Update: For OS X you need GHC 7.2 to use the LLVM backend. Otherwise GHC just ignores the -fllvm flag. The Haskell Platform only uses version 7.0.4.