I learned how to sharpen drill bits while I was a mold makers apprentice, lots of water passages in a plastic mold and almost all of them are cut with twist drills.
Lately that's what our refrigerator has turned us into - mold makers.
But seriously, folks, I'll have to say +1 to everything I've read on this thread about drill sharpening. There are some jigs out there that are great and the Drill Doctor works too, but if you can develop a good eye for what's needed just plain ol' hand sharpening will do just fine most of the time. Don't forget to have that water handy to keep it quenched.