Question: 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.

Answer: 
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)

<https://github.com/faylang/fay>
This language, **Roy**, is perhaps not really Haskell (?), but it seems very similar:

<http://roy.brianmckenna.org/>

Roy seems to be alive; there are many forks in the GitHub repo: <https://github.com/pufuwozu/roy>  

and it seems to be alive: <https://github.com/pufuwozu/roy/graphs>

If you're using Play Framework 2.0, then there's a plugin, **Ray**, to run Roy on Play Framework 2.0:

<http://brianmckenna.org/blog/ray>  

<https://github.com/pufuwozu/ray>

The last commit was four months ago, which is rather long ago keeping in mind that Play Framework 2 was released perhaps 4 or 5 months ago.