K-Meleon
K-Meleon Extension Setup (KMES): On the K-Meleon Extension Setup pages you can find a description of this extension setup system and more interesting for the users, a lot of extensions (some Mozilla extensions, for example) adapted for K-Meleon.
K-Meleon Extensions Central: http://kmext.sourceforge.net is the place where you will find many of the popular mozilla xpi extensions modified to work with K-Meleon as well as many other non-xul extensions written especially for K-Meleon.