RTorrent

Overview
rTorrent is written in C++ and uses the  library to provide a textual user interface. It can be used in a (SSH) terminal session together with a terminal multiplexer like, providing a very lean bittorrent solution.

Using its XMLRPC remote control API, alternative user interfaces can be provided by web clients like ruTorrent, or command line clients like pyrocore and its  command.

Useful Links

 * Installation Guide lists several ways to install rTorrent via packages or from source.
 * Commands Reference has a short explanation for all many of the configuration and XMLRPC commands (like this wiki, it'll get more complete if you contribute).