Wiki sites allow users to contribute content, quickly and easily, creating a collaborative, real time repository of information. See definition here – at Wikipedia, of course.
According to CFO.com, businesses are now exploring wiki technology as a means of sharing business and financial information without the complexity of content management software. Of course, by it's nature Wiki data sources can be edited and updated by any user. Yet this makes wiki technology perfect for collaborative development of proposals, obtaining feedback from employees, customers, partners, etc.
See also this list of Wiki corporate case studies at the socialtext.com site.
Office Collaboration, the Wiki Way
John Edwards, CFO.com
April 24, 2006