Who says Firefox is only about Web browsing? Plenty of extensions exist for letting you share files, chat with one another, meet new people, and call them -- all without leaving Firefox. Yet without a single page for collaboration or social networking on Mozilla's extension site, finding those extensions isn't easy.

Enter Networking Pipeline's crack researcher (that is, yours truly). He braved the toughest of the Web, scoured extension sites, and crawled through the underbelly of the Internet to find for you the absolute coolest collaboration and communication Firefox extensions around.

The selection criteria were simple. First, the software had to be a downloadable, publicly available Firefox extension. Second, the software had to be collaborative in nature. This means just what you'd expect: It had to allow two or more people to work together.

We uncovered 15 extensions that fall into five functional groups. Telephony clients let users call, and often IM, one another. Social searching and bookmarking extensions use social recommendations to help searchers locate Web sites of interest. Co-browsing coextensions turn Firefox into a tandem browser, and chat extensions let users text-message other users on a Web site.

Have we hit every collaboration extension for Firefox? Probably not -- the Web is a pretty big place, after all. So please e-mail me for inclusion in our next top Firefox collaboration extension list.