Since the beginning of AllPeers, there have been many different collections of plugins offering BitTorrent functionality to Firefox and its other Gecko-based variants of Flock, K-Meleon and Wyzo, a Mozilla Firefox-based browser that fully integrates BitTorrent functionality into its core along with Firefox 2.0 code.
There have also been numerous plugins as well:
AllPeers (http://www.allpeers.com)
FireTorrent (http://www.wyzo.com)
FoxTorrent (http://www.foxtorrent.com)
BitFox [...]