From HaskellWiki

Using Desktop Environment Config Modules

The following modules from xmonad-contrib make it easy to start with good basic defaults to work within the given desktop environment. They set up better communication between xmonad and taskbars or status bars through EWMH's, allow gap toggling, and rebind run and logout keys to sensible desktop environment defaults.

You will still need to set up your session management and tell your desktop environment (DE) to use xmonad as described in the DE specific documents on Xmonad, but the ff. will take care of getting xmonad's part of the puzzle working with a useful default configuration.

Start with the appropriate version below in ~/.xmonad/xmonad.hs then start or restart xmonad.hs to have xmonad recompile the binary in ~/.xmonad/ to use your new settings.

XMonad.Config.Xfce

import XMonad
import XMonad.Config.Xfce
 
main = xmonad xfceConfig

XMonad.Config.Gnome

import XMonad
import XMonad.Config.Gnome
 
main = xmonad gnomeConfig

XMonad.Config.Kde

import XMonad
import XMonad.Config.Kde
 
main = xmonad kdeConfig