Have you tried binsearch.info? This website also indexes NZBs for files hosted on the majority of newsgroups out there and holds them for up to 240 days to cover the retention period of some providers such as Giganews. Unlike newzbin.com, this site does not require any registration.
Another good Newsgroup search is the Newsrover application, which has the search built-in. It is very useful for finding smaller files on Newsgroups such as audio files. The catch however is that Newsrover requires annual registration ($30 for the first year, then $20 annually).
Note that no matter which newsgroup search provider you use, you will need a subscription to a binary Newsgroup provider to download anything. Your ISP may provide access, so it's worth checking with your ISP first.
Finally, before anyone else asks here, we no longer permit invitation requests to private forums/websites, as mentioned in this thread.