Yesod (most typesafe webframework), Stack (quick to become a very popular build/install tool in Haskell land), conduit (a lib/ecosystem for dealing with data streams), Stackage (publishes sets of packages know to work well together). He's currently Director of Engineering at FP Complete.

Here the packages he's a maintainer for on Hackage:

https://hackage.haskell.org/user/MichaelSnoyman