There's a new page that archives all the photos that have been featured on Picasa Web Albums. The page has a Media RSS feed, which can be added to any feed reader or it can be used as a source for Picasa's screensaver. If you don't have Picasa, you can view the images in a slideshow.
A great way to check the latest featured photos without visiting Picasa Web Albums is to add the image slideshow gadget to iGoogle. The gadget lets you view albums and search results from Flickr and Picasa Web, Google Image Search results and any Media RSS feed.