The qBittorrent project aims to provide a Free Software alternative to µTorrent. Additionally, qBittorrent runs and provides the same features on all major platforms (Linux, Mac OS X, Windows, OS/2, FreeBSD).
Transmission has the features you expect in a BitTorrent client: encryption, a web-based interface, peer exchange, UPnP and NAT-PMP port forwarding, web seed support, watch directories, tracker editing, global and per-torrent speed limits, and more.
µTorrent is a lightweight BitTorrent client that includes standard features such as bandwidth prioritization, scheduling, RSS auto-downloading and Mainline DHT. Additionally, µTorrent supports the Protocol Encryption joint specification and peer exchange.
FDM accelerates downloads by splitting files into sections and then downloading them simultaneously.