John's Background Switcher - Switch backgrounds to trending imgur, reddit, tumblr threads
PingPoint - Never miss a Mark Zuckerberg signup to your app ever again
Variety Wallpaper Changer - Variety is a wallpaper changer for Ubuntu which is featureful, yet slim and very easy to use.
ReIcon - ReIcon is portable freeware that enables you to save and restore your desktop layout.
Wallpaper Cycler - NuonSoft WallpaperCycler is a powerfull utility to manage all your wallpapers and to automatically cycle between your wallpapers.
AeroWallpaperChanger - AeroWallpaperChanger is another "wallpaper changer" software for Windows 7.