This is too cool to keep a secret...
Try a search in any American Memory collection with images (or a cross-collection search). You will see the familiar list of items. Above the list, there's a new option called "gallery view." It presents the results of your search in a thumbnail gallery -- a table with images across and up and down. You can easily toggle from the "gallery view" back to the "list view."
This just went on-line today and we're really loving it already.