NZBCat is an invite-only NZB site that has more than a million files indexed in their website. Free account members get 5 NZB grabs per day and 100 API calls.
NZBCat indexes content on Usenet using automated algorithms Users can use the web-based front end to search and browse for specific NZBs and add to any Usenet download application to get the content it refers to. NZBCat has been online since 2014 and has become one of the most reliable NZB indexers in the Usenet community.
Note: While releases are constantly updated, the website itself is quite outdated. It is evident on the news section of the homepage once you log in, where the welcome message was last posted in 2014. That being said, NZBCat still has a decent amount of NZBs indexed.