What games do you know that have impressive maps and modding made by the community? (PC games)
The most impressive I know is Stronghold (abbreviated SH). This sites have the best documentation and download about every trick in the game (they are numerous):
http://stronghold.heavengames.com/http://www.stronghold-knights.com/Basically it is a Castle Builder and Sieger. Although the map editor seems simple, it has many surprises and tricks. There are very versatile maps with effort made by the maps makers. The AI is weak but when you design and balance well a map, it can be challenging if you face a large army. The events script seems bad but there is lot of ways to suck out all of its potential.
There are tones of MBs in excellent enjoyable maps that are plenty of fun and eye candy.
For Rise of Nations (abbreviated RON), I haven't seen much but by the few, I think it has very powerful modding potential but most interesting tricks seem undocumented. The event scripter is actually done by programming the own game script. (you can make your own AI)
I don't about Starcraft (abbreviated SC) but the campaign editor is quite promising.
You kind find lots of modding and maps download from
http://www.heavengames.com/ sites. I haven't time to see the available stuff to all the games I have.
It is your time to share your games.