Thanks to Rebecca for sending an email around about this: the brand-spanking new LISWiki. From the About page:

LISWiki was established to give the library community a chance to explore the usefulness of Wikis. It is not intended to replace or detract from the Wikipedia Library and information science articles (or those in the printed LIS encyclopedias for that matter), but exist as a niche encyclopedia covering library-related issues.

I’ve already created an account for myself, as I’ve joined Wikipedia.