ABC is a free software, open source BitTorrent client based on BitTornado. It supports a queueing system with priority, global and local (per torrent) preference setting for downloading torrent (including upload and download rating limit), three upload options to do with completed file, and a system named Upload Rate Manager (URM) to force torrents out of queue if there is not a pre-set amount of upload activity. There is also an extensive web interface in ABC, allowing for other applications to view and change torrents and preferences remotely. 
ABC does not appear to be under development and thus appears to be dead software. The last version released was version 3.1 which was released on 2 October 2005.