I use these for NZB files, as well as the ones I get here (which are getting better all the time).

http://www.nzbsrus.com/

http://www.nzb-world.com/index.php

http://www.newzmonster.com/

http://newsreactor.net/index.php

http://www.nfonews.com/

Some, if not all have already been posted here but I thought I would put them all in the one place.