Other commenters have mentioned both Kerbal OS or MechJeb. Kerbal OS will let you geek out on programming your own routines while MechJeb will just handle the "boring stuff" for you like maintaining a particular vector while you do the "cool stuff" like navigation and mission planning. Some say these mods are like cheating, but once you can get a ship into orbit with your eyes closed, repeating that every time isn't really the fun part anymore.