Here are the sites that I use when I need a new brush.
http://www.psbrushes.net/index.php
http://www.deviantart.com/?loggedin=1#catpath=resources/applications/psbrushes&order=9&q=brush
http://www.psbrushes.net/index.php
http://www.deviantart.com/?loggedin=1#catpath=resources/applications/psbrushes&order=9&q=brush