Chat is by far the most popular type of collaboration extension for Firefox and the easiest to find (in small part thanks to the list of applications on Virtual Presence.org). These add-ons turn any Web site into a chat forum, for better or worse.
On the one hand, these applications allow for extemporaneous social interactions between people. Surfers can meet one another. E-tailers get to sell their site visitors. On the other hand, these extensions are in their infancy, often hampered by clumsy interfaces, questionable security, and nominal popularity.
The most unusual of the chat systems is Lluna from Bluehands, a German social networking company, with funding from SurfNet, the Dutch academic network. Though not a Firefox extension, Lluna uses a Firefox extension, Llunahelper, to shuttle URLs to an external application.
At first, I had a difficult time getting Llunahelper to run under Firefox. After much research, Bluehands' designer, Heiner Wolf, was able to reproduce the problem. The problem, he wrote in an e-mail, was that another one of my extensions, StumbleUpon (see below), somehow damages the browser's data structures where Llunahelper extracts the current URL from Firefox. "Since StumbleUpon also works with the current URL, I bet that they accidentally overwrite something," he wrote. The Llunahelper version 1.2 should correct the problem . "If not, then the general Firefox cache must be cleared."
Lluna presents avatars for the users viewing a site on the bottom of the Web page. Users can IM and chat with another, walk over to one another, use white-boarding tools to mark up a Web site, and co-browse the Web. Future releases will use VoIP so users can speak with one another. When that happens, Lluna users will likely be able to telephone with a large, pre-existing user base. The product is based on the XMPP protocol, the same protocol underlying GoogleTalk and Jabber. SamePlace is a chat extension also based on Jabber that uses a chat window in the sidebar instead of avatars on a page.
2006 Netmite Communities 2.2 adds a Firefox sidebar that allows users to post and review comments about a Web page. Users can also participate in group or individual discussions tied to or separate from a Web page and rank other user's postings. Personally, I found Netmite's interface to be clunky, but there's probably no other chat client that competes with its functionality or traffic volume.
Ajax is starting to be put to good use by some extension developers. Gabbly is an Ajax-based chat extension that runs as a Firefox sidebar. It's unique in that it delivers transcripts of the chat session by RSS. Chatsum is also a slick-looking AJAX-based client that provides an easy way to find other chatters.
With the Yakalike extension, users navigate channels associated with each Web site in a frame at the bottom of their browser. Channels can be found by clicking on the "popular-channel" button or by simply viewing the site where a small window lists the users on the site.
For those IRC diehards, the Peeko Chat extension adds an IRC text bar at the bottom of the Firefox window. Site viewers can see who else is on the same Web page and then chat with one another through text commands. Alternatively, they can launch ChatZilla, a Firefox extension that runs as an external client for chatting on the IRC service.