http://www.codewars.com/ is a site where code kata can be practised in a variety of languages.
Kata are real code challenges focused on improving skill and technique. Some train programming fundamentals, while others focus on complex problem solving. Each kata is crafted for and by the community.
This project holds the Haskell Kata I have worked on in online Haskell IDE www.fpcomplete.com
I also use Light Table IDE with a Haskell plugin as a REPL