Open Source for Mac OS X

Transmission is designed from the ground up to balance power with simplicity. We've set initial preferences so things "Just Work", while advanced features like watch directories, bad peer blocking, and the web interface can be configured with just a few clicks. When Ubuntu chose Transmission as its default BitTorrent client, one of the most-cited reasons was its easy learning curve.

Transmission has the features you expect in a BitTorrent client: encryption, a web interface, peer exchange, DHT, UPnP and NAT-PMP port forwarding, web seed support, watch directories, tracker editing, global and per-torrent speed limits, and more.