Readarr is a ebook (and maybe eventually magazine/audiobook) collection manager for Usenet and BitTorrent users. It can monitor multiple RSS feeds for new books from your favorite authors and will grab, sort and rename them.
NZBHydra is a meta search for NZB indexers. It provides easy access to a number of raw and newznab based indexers. You can search all your indexers from one place and use it as an indexer source for tools like Sonarr, Radarr or CouchPotato.
SABnzbd is a multi-platform binary newsgroup downloader. The program works in the background and simplifies the downloading verifying and extracting of files from Usenet.