Although I have found it inconvenient for users (and me) to have interactive widgets on this blog, one of these might be useful for a wiki page as it could be more self-contained.
Suggestions from the Webhead elist include (from Robert Squires):
Yackpack - the Walkie Talkie Widget formerly available directly on PBWiki, and which has Voicegroups.
Meebo - you create your own chatroom and paste the code into the sidebar of your wiki or blog.
Gabbly - the PBWiki default, was mentioned several times as having horrible advertisements that you can't get rid of. However, any person who visits the wiki can chat with other visitors who are there at the same time while with Gtalk or Meebo, the visitors can only chat with the owner of that widget (ie.e, the creator of the wiki) but not with each other (per Negiz in a responding email).
Robert also offered an interesting blog site with a list of ten more chat widgets: ReadWriteWeb.
I followed this breadcrumb trail and found an interesting site, built by Kiernan, that strings together YouTube videos so that you get continuous play, one after another, on a particular subject (in this case rock groups). Anyone can add a video without a password, though this feature might present problems in a school setting. Nice code, though a little removed from the original subject, chat widgets: http://www.chann3lz.com/.