For what purpose do you use a Wiki within your organization?

Internally, we use our wiki everyday and are encouraged to do so as an international organization as it is light-weight and easy to use; whilst being available to the entire company. We tend to keep away from using it for storing project deliverables, but do use it for storing snippets of information about a project - the stakeholders, who's who internally, etc on a project as well as the FAQ's for development builds, releases and testing. For our project artefacts and deliverables, we are using our own bespoke Java applications alongside regular Microsoft products like Office and Project. From a company administration perspective, we use it to keep track of internal initiatives; people's professional experiences outside of our company and their skills (wiki's search capabilities help us find internal knowledgeable resources when we have questions); as well as internal function processes such as expense claims and HR, etc. PS - currently within our organization we use docuWiki.

Question Details:--------------------
For what purpose do you use a Wiki within your organization?How often and for what purpose do you use an internal company Wiki within your Software Development Organization? Do you use it to share knowledge, describe processes, document your developed Software, make plans and estimates, etc. Or do you use another system for such things? Also, which Wiki do you use?