Also, check out my NZBFeeder application on http://sharputils.blogspot.com/
It enables you to hook up to RSS-feeds from NZB-sites, and (if they support it) automatically have it download NZB-files according to rules you specify. With built in episode-tracker for TV-shows.
Currently in beta, but it seems to work.
Newsleech, Bintube, FST and Binsearch.
Why would anybody use anything other than Newzbin? I can't think of any other site as comprehensive or easy to use.