Forums of the Megaverse®

The only official maps are in the books, the best are in the Rifts GMs guide.
If you want to see some online, look for unofficial fan maps, some of them are pretty good and actually contain more data than the official ones.

umm, just search around these boards, the web ring or google it.
Here's a start, it's a link to a similar previous discussion;
viewtopic.php?t=22416&highlight=maps