Everyone has probably checked out graaldepot.com at some point.

Another good site is charmheart.wordpress.com - if you look on the friends tab you can usually find some other sites to check out as well

To upload customs, go to era-go.com/upload

Don't forget to check the upload rules so you won't be disappointed if an illegal custom is denied: http://era-go.com/forum/showthread.php?209-Upload-Rules