I was curious to see how you guys n gals handle dungeon maps at your roleplaying sessions.

Do you show maps to your players?
Just for encounters?
For the entire dungeon?
If there are more rooms than they can see (secret rooms, rooms behind doors) do you trust your players not to metagame or do you cover the invisible areas somehow?

For me, I've used full dungeon maps only as a reference for myself, and battle/encounter maps I usually scribble on paper on the spot if players want to know where everything is (we kind of wing combat at our table).
But now that I'm getting into DD3 I'm making some maps that could actually be of use to my players, plus they aren't crappy enough for me to want to hide them.

Obviously if you game over the internet this is not really an issue, since FantasyGrounds can mask whatever area of the map you want, and I'm sure similar applications have a similar feature. For actual physical tabletop gaming though, I'm at a loss. The only solutions I can come up with involve a) a truckload of Post-Its and/or b) a lot of duct tape.

So how do you handle this?