InfoWorld has a good primer on the use of wikis and blogs within an enterprise. While for someone who has been around blogs and wikis for a while none of the information will seem new, it is a great introduction for new people. If you are looking to get them introduced into your company forward the link to others.
However what is useful for all is their Blog and Wiki Best Practices which can be viewed here. I have summarised below.
1. Choose the right tool
2. Enhance existing processes
3. Encourage honest and open voices
4. Establish policy
5. Support successful blogs
6. Plan for leaks
7. Review content regularly.