The first places that come to mind to check out are (in no particular order):
http://www.ar15.com/
http://www.homegunsmith.com/cgi-bin/ib3/ikonboard.cgi
http://www.cncgunsmithing.com/
http://www.falfiles.com/forums/index.php
I'm sure there are others but this should get you started.
Welcome to the addiction.