SymTorrent – A torrent client for the 2nd and 3rd generation of the Symbian OS; supports downloading of multiple files simultaneously, resuming after restarting the application and more.
Transmission – Transmission is a torrent client directed at Mac OS X, Linux, FreeBSD and Solaris, and with the use of a web UI (Mac version pictured above) named Clutch, you can control it from your mobile phone. Some people have reported getting Transmission to work directly on their phones, but apparently not everyone has been able to pull it off.
uTorrent iPhone – An interface to control your torrents on the µTorrent web UI.
WickedPsyched iPhone Torrent – Not for the non-technical among us, the folks over at WickedPsyched have been working on getting a Linux-based torrent client to work on the iPhone in command line form. It’s still buggy, but they’re getting there.
WinMobile Torrent – Made for any device running Windows Mobile version 5 or 6. It is a paid download, but it will give you all the usual features you would expect from a torrent client: leech, seed, check for scraping and more.