Web
The web development community in Haskell has recently had a large boost in activity, resulting in a plethora of choices in libraries. As usual, a breadth of options is a double edged sword: you can choose the tools more to your style, but it is harder to find quality tools.
You may want to start on this wiki by looking at Web/Frameworks.
Please join us on the mailing lists to discuss web development in Haskell.