The qBittorrent project aims to provide a Free Software alternative to µtorrent. Additionally, qBittorrent runs and provides the same features on all major platforms (Linux, Mac OS X, Windows, OS/2, FreeBSD). qBittorrent is based on Qt4 toolkit and libtorrent-rasterbar.
qBittorrent Features: Polished µTorrent-like User Interface Well-integrated and extensible Search Engine Simultaneous search in most famous BitTorrent search sites Per-category-specific search requests (e.g. Books, Music, Movies) All Bittorrent extensions DHT, Peer Exchange, Full encryption, Magnet/BitComet URIs, ... Remote control through a Web user interface Nearly identical to the regular UI, all in Ajax Advanced control over trackers, peers and torrents Torrents queueing and prioritizing Torrent content selection and prioritizing UPnP / NAT-PMP port forwarding support Available in ~25 languages (Unicode support) Torrent creation tool Advanced RSS support with download filters (inc. regex) Bandwidth scheduler IP Filtering (eMule and PeerGuardian compatible) IPv6 compliant Sequential downloading (aka "Download in order") Available on most platforms: Linux, Mac OS X, Windows, OS/2, FreeBSD