The other day sprite managed to splatter on my Droid, gumming up the slide mechanism. I simply cleaned off what I could, then applied small dabs of grease in various areas, before sliding it open and closed a few times, letting it get under the panel. I then wiped off any excess that wasn't obviously lubricating, and it's now 100% smooth, sliding better than before the incident occurred.
IMO, the sliding mechanism isn't specialized enough to require any unique brand or safe lube. I just used some stuff that I typically apply on nuts/bolts when working on my cars, and it worked fine. If you don't have anything at home that can lubricate it, try a hardware store or something...they should have something small and cheap that you can apply (provided this is your issue).