MuggleNet has a brief report from the set of Harry Potter and the Prisoner of Azkaban.
We asked the guard if we could go in, but we weren't allowed. He said that the only actors there today were Crabbe and Goyle and the extras. We stood and watched for a minute as they finished their scenes, then all the extras, including Crabbe and Goyle, left for their lunch break.
There weren't a lot of people there today, as the actors weren't there, but the guard told us that Tom Felton would return to the studio next week. The crew is packing up now, and will leave by tonight.