Ross Mayfield and his team have put together a really interesting and powerful tool. In many ways, Socialtext is one the closest things currently out there to a full blown Web Office solution in that it is already been used by some very large instituions, including Dresdner Kleinwort Wasserstein, Nokia, and Ziff Davis Media. Socialtext have email integration - you can email content into the Wiki. They also have put together a complete Socialtext appliance solution, making very easy for a conservative, security minded company to get up and running with minimal internal delays.