Azureus implements the BitTorrent protocol using java language and comes bundled with many invaluable features for both beginners and advanced users:

    * Multiple torrent downloads
    * Upload and download speed limiting, both globally and per torrent
    * Advanced seeding rules
    * Adjustable disk cache
    * Only uses one port for all the torrents
    * UPnP sets the forward on your router
    * Can use a proxy, for both tracker and peer communications
    * Fast resume
    * Can set a default download dir and move completed files
    * Can import torrents automatically from a set dir
    * Highly customizable interface
    * IRC plugin included for quick help
    * Embedded tracker, host your own torrents, automate your shares (periodic scanning of a dir)...
    * Distributed Hash Table: host on it a completely decentralised torrent and/or benefit from it when the tracker is offline.