I learned to know the Wiki Wiki Web when searching for information about Design Patterns and Extreme Programming.
I work for Canoo Dot Com in Basel, Switzerland Country.
Wiki Quick List:
c2.com 
We use a local installation of the Wiki Wiki Web with some minor modifications. Out we use our Wiki Wiki Web as
corporate knowledge base
for discussion / feedback on proposals
up-to-date information on "who is where" and current occupations
and even for capturing and management of stories and tasks like in the XP Planning Game
What we found useful:
access wiki through https for ubiquitous but still private usage
synchronize Recent Changes as an offline page with depth 1 for an offline (read-only) version of wiki
send wiki pages via mail for additional "push"es of information
Additionally there is a wiki to provide an interactive help system for Xp Plan It, a tool for capturing the Planning Game.
contributions: Xp As Trouble Detector, Continuous Integration Applied, Xp Plan It, Canoo Web Test, Ultra Light Client Java, Collaboration Tools, Xp Adopters Group Switzerland, Early Profiling, Lazy Optimization, Test Coverage, Drawing Hand, Can Functional Tests Replace Unit Tests, Mock Object, Else Considered Smelly, Is Xpa Process, Infrastructure In Xp, Dont Limit Your Options, Can An Architecture Emerge, What Makes Discussion Groups Effective, Ruby Test Unit, Wiki Migration, Ruby Test Unit
See original on c2.com