Question: Do you know any online problem sets or contests that accept solutions in Haskell? I know only [El Judge](http://acm.mipt.ru/twiki/bin/view/ELJudge/WebHome), but unfortunately it has some problems with ghc, so any Haskell problem is rejected with "memory limit" resolution.

Answer: 
* [exercism](http://exercism.io/) has exercises in Haskell.
* [CodinGame](http://www.codingame.com/) accepts.
* others like [UVa Online Judge](http://uva.onlinejudge.org/), Google Code Jam, Project Euler and etc, don't require a specific programming language.

Additionally, there's the [Programming Contests](http://www.haskell.org/haskellwiki/Programming_contests) page in Haskell.org.
* [HackerRank](https://www.hackerrank.com/environment): HaskellPlatform 2013.2.0.0 + logict lens pipes mwc-random hashtables regex-pcre hmatrix aeson and hashmap libraries
* [HackerEarth](http://www.hackerearth.com/docs/judge/#language-compilers): GHC 7.4.1