OpenWRT http://openwrt.org/ also has a number of clients (and even a tracker) ready to be installed in the repository:

  # opkg list | grep -i torrent
  btpd - 0.15-1 - BTPD is a bittorrent client consisting of a daemon and client commands,
   The daemon is capable of running several torrents simultaneously and only uses one tcp port. 
  cbtt - 20060727-1 - Bittorrent tracker
  cbtt-mysql - 20060727-1 - Bittorrent tracker (with mysql support)
  ctorrent - dnh3.3.2-5 - CTorrent is a BitTorrent client written in the C programming language,
  ctorrent-nossl - dnh3.3.2-5 - CTorrent is a BitTorrent client written in the C programming language,
  libtorrent - 0.12.6_r1130-3 - LibTorrent is a BitTorrent library written in C++ for *nix, with a focus
  rtorrent - 0.8.6_r1130-1 - rTorrent is a BitTorrent client for ncurses, using the libtorrent library.
  transmission-daemon - 1.92-1 - Transmission is a simple BitTorrent client.