The Guardain is one of the better models of a paper that has effectively transitioned to the web. They are big fans of Q&A and use it in many ways. In their Life and Style Series they interview a wide variety of famous people asking them the same questions: “What is your greatest fear”; “What is your earliest memory”.
In other section they provide what is basically a primer or FAQ about current subjects: What is carbon capure and storage and how does it work. It’s worth having a look at their section on the envriroment called: Q&A The Issue Explained.
Then there is the expert Q&A where readers get to ask questions. You can see this in their Money section: called Our Experts.
I think that is the most effective and varied use of Q&A I have seen on a single site. If that weren’t enough, one of my favorite bloggers, Jeff Jarvis of BuzzMachine also writes a regular column for the Guardian.