You can configure the visual effects (collage, wipe, pan and zoom, cross fade) and how often the photos change. The title and the author of a photo is always visible and you can go to the source of the photo by clicking to one of the links from the bottom of the window. The screensaver acts like a slideshow so you can move to the next/previous photo using the mouse. To add a new source, right-click a link to a feed in IE and Firefox and select 'Add to Google Photos Screensaver'. Some nice feeds: Flickr ( Vista wallpapers, nature, architecture, landscape, Google food), Yahoo search ( autumn, Dali, sunset). You can find them in photo sharing sites like Flickr, Picasa Web Albums or at this page. It's probably the most interesting feature of Picasa Web Albums: you can monitor all the photos uploaded to your contacts' albums.
If you use Google's photo sharing site, you can view pictures from the most recently modified albums and from your contacts. You select a list of folders that contain photos and Google Screensaver monitors the JPEGs from these folders. Google Screensaver is a Windows screensaver that displays photos from different locations: Update: The screensaver is now a Picasa feature.
