taffybar - A slightly fancy status bar for xmonad
The bar is configured much like XMonad. It uses ~/.config/taffybar/taffybar.hs as its configuration file. This file is just a Haskell program that invokes the real main function with a configuration object. The configuration file basically just specifies which widgets to use, though any arbitrary Haskell code can be executed before the bar is created. See full documentation of release version here.