Are there any good map generators out? I really like Oasis that comes with the game. I'd be very happy if someone had a set of Rise of Nations-style map generators.

There are 2 user made map scripts that I know of.
One is mine (http://apolyton.net/forums/showthread.php?s=&threadid=145842 also a thread here http://forums.civfanatics.com/showthread.php?t=149278) and there's also surt.py here http://apolyton.net/forums/showthread.php?s=&threadid=145783

I never bothered much with RoN, what are the map generators like?
I know there are utilities (external programs) to turn a (set of) bitmap(s) into a map, so these are map generators too.

I do have the tectonics mapmaker, but I can't play on maps bigger than small until my video card starts working, so I'm sticking with the entirely land-based map styles (Oasis is my favorite, but Great Plains and Inland Sea are good too). Oceans bad!

RON had several different map styles which dramatically changed the game played. There was

East Indies (archipelago)
East v West (teams on different continents)
African Watering Hole (plains, with resources clumped in the center)
Amazon Rainforest (mazes of jungles)
Himalayas (tons of mountains and forests)
Mesa (open spaces with mountains, few forests)

and a bunch of others