The _khAttAm_ blog posted a quick tutorial about disabling the Unity interface in Ubuntu 11.04

Unity interface is the default interface in Ubuntu 11.04 Natty Narwhal. However, if you don't like the dock, animations and the interface as a whole, you can just disable the Ubuntu Unity Compiz Plugin and Unity Interface will be gone. To do that, install Advanced Desktop Effect Settings from Software Center (or compizconfig-settings-manager from Synaptic or apt-get command) and then launch it by pressing Alt+F2 and typing in ccsm.

  Disable Unity Interface and restore original interface in Ubuntu 11.04