HollywoodIndustry.com is running an article on the VFX of Harry Potter and the Chamber of Secrets. VFX Supervisors Jim Mitchell and Bill George, along with Animation Supervisor David Andrews of ILM explain how some of the VFX, like Dobby and the Quidditch match were brought to life. Also discussed is the work by MPC and Framestore/CFC.
You can read the article here:
Thanks to Ian Failes, who spotted the reference at CGChannel, for providing the great link.