I'd be interested to hear if anyone has solved the problem of embedding a series of pages inside of another (in the sense of Seaside) in a pure functional way. In other words, here's my challenge: write http://www.seaside.st/about/examples/multicounter using the same monadic style.
Except that these two code examples do two very different things. The Haskell version actually uses a continuation to run multiple requests The Javascript version modifies local mutable state. The Haskell version does it via server interaction, which makes it much more useful to modern web apps.
No, really. Web programming and continuation monads seem to have really it it off together. When you add them to another language, you get similar results (e.g., http://intensivesystems.net/tutorials/web_sessions.html).