For the ASCII characters, there's
this and
this.... but to type in ASCII, hold the Alt key, and then type the three-digit decimal code, then release the Alt key. EXAMPLE: Alt + 188 = ╝
Here is a list of
official TF2 maps.
Here is a list of
popular unofficial maps.
But those are just lists.
Go to
TF2 Maps' Download page to download community-made maps, or go to
Gamebanana to submit your own for anyone to upload. TF2Maps frequently hosts mapmaking contests, and some of them have gone on to be official content.
As far as casual/comp groups, there are plenty of TF2Newbs groups, so IDK if we need another one, but perhaps you can try
the 2Fort one. Or you can create your own group of friends if you can consistently find some willing to play at the same time....