aria2 is a lightweight multi-protocol & multi-source command-line download utility. It supports HTTP/HTTPS, FTP, SFTP, BitTorrent and Metalink, etc.

BitLord is a free, ad-supported and proprietary BitTorrent client for Microsoft Windows and macOS.

Deluge is a lightweight, Free Software, cross-platform BitTorrent client.

FilePizza is a free peer-to-peer file transfers in your browser.

Folx is a download manager for Mac OS X. It integrates with the Mozilla Firefox, Safari and Google Chrome web browsers and with the FlashGot extension.

FrostWire is a free, open source BitTorrent client.

BitComet is a BitTorrent/HTTP/FTP download client and supports many modern bittorrent protocol, e.g. Magnet Link, HTTP Seeding, DHT network, UDP tracker, etc.

itTorrent is a communications protocol of peer-to-peer file sharing ("P2P") which is used to distribute data and electronic files over the Internet.

Downpour helps you find downloadable audio books.

Flud was a social news reader application for iPad, iPhone, Android and Windows Phone.

Free Download Manager accelerates all types of downloads (files, video, torrents).

Halite (named after the mineral) BitTorrent client based on the excellent libtorrent library.