Weighing in at a mere 8.1 KB, Artlav's new InterMod autopilots module packs a lot of punch. Just updated for Orbiter 2006, this add-on is simply a small DLL that gets activated in the Modules tab of the Orbiter launchpad. It doesn't require an MFD and doesn't have any on-screen display (other than a switchable debug readout in the lower left corner of the screen).
What it adds is several new autopilot command keys analogous to Orbiter's built in ones such as kill rotation, horizontal-level, and auto hover. One is "kill translation" (numpad-7) which is an analog to kill rotation (numpad-5) and which zeroes out translation components relative to the nearest vessel. Other keys include V for vertical auto-hover (used to hold a "tailsitter" spacecraft which lacks hover engines in an automatic hover using the main engines) and C which holds vertical orientation (i.e., nose pointing at zenith, typically used with V). There are also finer resolution controls for hover engines and a few other features. Simple but elegant.