I figured out how to glitch the maps in multiplayer. (yes, i find this interesting.)
Classic: You can use your Light Cycle to get on top of the map. Hard to explain how, I'll think of a explanation laterz. I got near Sark's Carrier up there. WAS AWESOME.
User's Plaza: The parts with Clu's orange barriers are extremely weak. You can use your Light Cycle on them to get out of the map. Stand in front of a barrier, jump, and in mid-air activate your Light Cycle. When you do that use the turbo boost to drive up the barrier once. Then let go and grab onto the top of the barrier. After doing that get on your Light Cycle and do a few more turbo boosts. (usually two or three) Then jump off your Light Cycle and your off the map! It's pretty cool to explore. Just don't go to far or you'll derezz.
Relic: The parts with rock[?] jutting out of the wall are weak. Drive up those parts of the wall like I explained in User's Plaza. When you jump off you'll be in mid-air. You'll need to drive up the wall again and jump to get off the map. Be really careful when doing this because it's easy to derezz there.
I'm exploring other ways to glitch to. And no, I don't use this to cheat. I do it by myself or with other people who like to glitch. (and it's impossible to cheat when your outside the map anyways.)
note: I've discovered that the background objects, outside the map, are solid.
Will put more notes up when I find them.