Theres generally contests held over here: http://boards.polycount.net/forumdisplay.php?f=47 All the mini-comps were put on hold for DWIII, but nothing has been started back up since it finished it seems.
in the Contests and Challenges forum. http://boards.polycount.net/forumdisplay.php?f=47 there are usually weekly/monthly challenges but the Dominance War has occupied most people for the last 2-3 months. things should be back to normal in a couple weeks or so when everyone has had a rest.