Azureus is a free Java based BitTorrent client
BSEditor: Azureus is a Java based BitTorrent client that offers multiple torrent downloads, queuing/priority systems (on torrents and files), start/stop seeding options and Instant Access to numerous pieces of information about your torrents.

Azureus is a BitTorrent client with multiple torrent downloads and instant access to information.

Azureus also features an embedded tracker that is easily set up and ready to use.
New Features:

Core | Reduced CPU usage, especially in some unusual conditions
Core | Explicit local subnet and peer injection option for Lan Peer Finder
Core | Auto upload speed
Core | DND completion handled better
Core | Added option for per-torrent max upload speed when upload busy
Core | Ranges allowed for port listing to ignore peers from.
Core | Added option to move completed download on removal
Core | Signed updates for increased security
Core | UDP fallback on connection FAIL
Core | Support for initial crypto tracker spec
Core | FASTER queued torrent startup
Core | Option to disable tracker support for full-scrape
Core | Added ability to rename the directory save name for a multi-file torrent
UI | File pieces shown in files view
UI | Ability to best Guess folder you want to save torrent data to based on existing torrents
UI | Filter for Config Options
UI | Help -> Generate Debug Info to help us solve bugs
UI | Ability to customise the speed intervals for download / upload speed menus
UI | Ability to rename the displayed title of a download
UI | date added, idle up, idle down, req in, req out colmns added to MyTorrents
UI | manual file recheck order
UI | Option to remember passwords
UI | OSX: Open .torrent files into Azureus via Finder/Desktop/etc
UI | Option to send popup message when download of a torrent (or individual file) has completed
UI | Ability to change behaviour of popups: auto-hide behaviour and adding timestamp to messages you can free download Azureus 2.5 now.