There is a neato video showing some of the CG compositing used by Rising Sun Pictures on Harry Potter and the Half Blood Prince. RSP is one of the many success stories in the industry for Australia and their work is top notch as shown in the vid. Seeing how much complexity there is in these shots just gives me all the more admiration for the craft.
There are also videos for Wolverine, Terminator Salvation a host of others on their Portfolio Page.
[Image from the Breakdown for Harry Potter HBP from Rising Sun Pictures]