I use Tmux for split panes and windows. Brian Hogan wrote a great book on Tmux called tmux: Productive Mouse-Free Development. You should read it.
I use a number of vim plugins:
- haskellmode-vim for _ t and _ T (show type and insert type), among other things.
- ghcmod-vim for HLint and HCheck, also used by Syntastic and NeoComplCache.
- neco-ghc uses ghcmod-vim for nifty Haskell completion, powered by neocomplcache.
- Syntastic automatic syntax checking for vim.
I also use guard and guard-shell to automatically compile and run tests. Here's my Guardfile.