Dark Viper, Icky, and I played on some player made maps yesterday. I was surprised at the high quality of them. Check them out and give them a try.

Planet CoH map database
Relic Map Contest Winner Pack (winners from the Relic map making competition)
Relic Forums Finished Map List

I will list the instructions here for playing new maps since it took me a while to wade through to find the correct information.

1. Open Windows Explorer and find the directory where you installed Company of Heroes.
2. Go to x:\Company of Heroes\WW2\Data.
3. Create a new folder called Scenarios.
4. Go into the Scenarios folder and create a folder called MP.
5. Place any map into the MP folder with it's own folder name. What name you give the folder does not affect the map info displayed in-game.
6. Make a new shorcut for Company of Heores on your Desktop. Right-click the new icon and select Properties. In the box that labelled Target, add -dev to the end of the line after the quotation marks. Hit the OK button at the bottom. Right-click the icon again and select Rename. Rename it so you can identify the shortcut as the one with the additional command. You can only play with other CoH players using the same command so non-dev players cannot play with -dev players. You need to use the -dev shortcut to play the user created maps or they wont show in the maplist.

Note: These instructions are for the maps that use .sgb format, not the .sga format. The easiest way to tell is that .sga is only one file while .sgb comes with additional supporting files. You need to make a folder to put the .sgb and it's companion files but you do not for .sga. I have yet to find instructions that work for the .sga files.