I'm doing a feed reader type of application for torrents. Something to give you a sound when it's sitting in the tray and a new torrent shows up on one of your categories of choice.
This will be done in Delphi or FreePascal when it's solid.
My question is due to the possible need to integrate a BT client in the future.
You should check out this project at SourceForge. I'm not sure how good it is, but it's in Delphi.
I've found this one: Torrent Torque
Unfortunately it looks like development has halted after getting the BEncode classes done.
I've also found this one: Total Torrent
It's a bit more evolved. It has classes in place for the actual Blocks/Pieces and some code for threads.
I'll investigate the code in more detail and edit this answer with some more information.