Azureus:

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.

*Many useful plugins are available:

*Auto-adjustment of your upload and download speeds according to your network charge with Autospeed
*Auto-download torrents with RSS Feed Scanner
*Schedule upload and download speed limits with Speed Scheduler
*Receive a mail when a download finishes with Status Mailer
*Add numerous info on torrents (Extra seeding columns, Country Locator)
*Remote control Azureus through the Swing Web Interface