Dangerous Journeys / Mythus had a map of Inner Aerth that covered the whole inside of the planet. I don't remember where I last saw it online though.. :/
The Mystara setting had a hollow world, you can probably find the map online some where.
do a google image search for "hollow earth"
Inversia (http://www.worlddreambank.org/I/INV.HTM) or Abyssia (http://www.worlddreambank.org/A/ABY.HTM) at the World Dream Bank.