qBittorrent is a C++ / Qt4 Bittorrent Client which was created in March 2006 with the idea of developping a new Bittorrent client for Linux that would be easy to use, good looking, featureful but lightweight.
qBittorrent is an attempt to provide a Āµtorrent equivalent on Linux. It is a Free Software released under the GNU GPL license. qBittorrent is based on Arvid Norberg’s libtorrent-rasterbar.

qBittorrent features

qBittorrent can now be considered as a good alternative to other bittorrent clients. It provides a lot of features such as:

* A polished Graphical User Interface written with Qt4 toolkit
* UPnP / NAT-PMP port forwarding support
* Encryption support (compatible with Azureus)
* Multiple simultaneous downloads / uploads
* A well-integrated search engine
* DHT (trackerless) support
* uTorrent Peer eXchange support (PeX)
* Directory scanning with automated download of torrents inside
* Good internationalization (~25 languages supported)
* Selective download of files in a torrent
* Media File previewing while downloading
* Torrent trackers edition and prioritizing
* Seeders / Leechers displayed in download list
* Styles support
* Files prioritizing in a torrent
* Torrent download in correct order
* System tray integration
* Tracker authentication support
* Unicode support
* Torrent downloading directly from their url
* Connection though a proxy
* IP Filtering similar to the one in eMule or PeerGuardian
* Allow to buy your downloads thanks to Sharemonkey
* Torrents queueing and prioritizing
* Web user interface for remote control
* ĀµTorrent spoofing to avoid ban
* Magnet URI support
* Automatic download from RSS feeds with advanced filtering
Install qbittorrent in ubuntu 9.04

First,edit sources.list:

sudo gedit /etc/apt/sources.list

add this two lines,then save and close it.

deb http://ppa.launchpad.net/hydr0g3n/ppa/ubuntu jaunty main 
deb-src http://ppa.launchpad.net/hydr0g3n/ppa/ubuntu jaunty main 

Add GPG key by this command:

 sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 47B4D1C4

Update and install:

sudo apt-get update
sudo apt-get install qbittorrent

Now,you can launch qbittorrent from Applications->Internet->qBittorrent