I've seen floppy drive cleaning kits kicking around the dollar stores, still. They seem to consist of a normal 3.5" floppy casing with a "disk" made out of fabric, and a small tube of liquid. You apply the liquid to the "disk" and insert it into the drive. This probably cleans the heads, much like the audio cassette cleaning tapes. I have no experience with using them, so I can't advise whether this is a good idea or not. In any case, it would be a step after removing dust bunnies.