I just learned that you can have your good knives professionally sharpened at Strosniders' Hardware in Bethesda. I guess the service is done Tuesdays and Fridays. If you drop them off the day before (Monday or Thursday, obviously) you can pick them up after 5PM the following day. I've not done it myself yet, but an officemate raved.
Btw, this is an incredible store if you've never been there. I had been looking for a fish grill-basket for a year, and found the perfect one on their shelves. It's big enough to hold a large, whole fish. It's non-stick. And the long handle is removable so that you can close the grill lid. (And the store is right around the corner from A&H Seafood, so you can stop in there and pick up your fish! It's also just down the street from the Bethesda Farmer's Market -- Weds and Sats I think.)
Strosnider @ 6930 Arlington Rd. (301)654-5688.