I built a shell in Haskell for a class project this semester. At some point I'll get around to releasing it on Github. It doesn't do much aside from backgrounding tasks, piping, and supporting environment variables (both in a config file and dynamically through a built in export command). But it was fun to build!
I would totally use something that allowed me to use Haskell like I use bash. Turtle allows me to do some of it. I'm thinking more along the lines of this project that never took off though:
