deluge is a lightweight, Free Software, cross-platform BitTorrent client.
nntp2nntp proxy allow you to use your NNTP Account from multiple systems, each with own user name and password. It fully supports SSL and you can also limit the access to proxy with SSL certificates. nntp2nntp proxy is very simple and pretty fast.
nzbget is a usenet downloader, written in C++ and designed with performance in mind to achieve maximum download speed by using very little system resources.
pyLoad is a Free and Open Source download manager written in Python and designed to be extremely lightweight, easily extensible and fully manageable via web.
The qbittorrent project aims to provide an open-source software alternative to µTorrent. qBittorrent is based on the Qt toolkit and libtorrent-rasterbar library.
sabnzbd makes Usenet as simple and streamlined as possible by automating everything we can. All you have to do is add an .nzb. SABnzbd takes over from there, where it will be automatically downloaded, verified, repaired, extracted and filed away with zero human interaction.
transmission is designed for easy, powerful use. Transmission has the features you want from a BitTorrent client: encryption, a web interface, peer exchange, magnet links, DHT, µTP, UPnP and NAT-PMP port forwarding, webseed support, watch directories, tracker editing, global and per-torrent speed limits, and more.