I've tagged content on wikis at:
http://del.icio.us/just_tonya/wikis
the overall category


Some subcategories:

Corporate wikis: http://del.icio.us/just_tonya/corporate
Examples of wikis: http://del.icio.us/just_tonya/wiki
Introductory info: http://del.icio.us/just_tonya/introductory
Wiki adoption: http://del.icio.us/just_tonya/adoption
Wiki engines: http://del.icio.us/just_tonya/engines
Wiki hosting: http://del.icio.us/just_tonya/hosting
Wikis in education: http://del.icio.us/just_tonya/education