I am not looking for a necessarily super-robust solution with a 10-year track record, but for something that can be used in a real applications, and goes beyond just being able to run an Hello World example.
My preference is to run the compiler on the server, so I can compile Haskell code ahead of time. Of course, the solution would need to be more than just a compiler, and enable Haskell code to access the API available on the browser (DOM, XHR…).
Footnote: the projects I have seen so far don't seem to be actively maintained, or to go beyond being able to run "Hello world", or in some case even to go beyond a project description.
There is a more complete list here:
http://www.haskell.org/haskellwiki/The_JavaScript_Problem
and there is also Fay (although it is only a subset of haskell)