Here's a really cool find: MuggleNet reader Cami sent us a link to the website of Adam Brockbank, a conceptual artist for many films including the Potter series. Within his site you can find lots of concept art for Chamber of Secrets through Order of the Phoenix – everything from mopping house elves to beautiful views of Hogwarts.
To check it all out, visit his site right here, then click on Concept Art. From there, you can select any of the films he has worked on. Also be sure to visit the Storyboards area, where you can see some work from Sorcerer's Stone.
Thanks again to Cami for the tip!