µTorrent is very very light weight bit-torrent client. It's amazing for poor peoples like me, who don't have much money to buy enough RAM. Installer is 130 KB and the application takes only 5-8 MB in my RAM. It's all those features which an advanced bit-torrent client should have. So, I kicked Azureus out (takes 30-60 MB RAM) and µTorrent is in.
Get it from here.