These are the 2 most common used programs for Dual++ Display lovers.
1. Display Fusion
It offers a free and a comercial use version. Managing Wallpapers, timers, and most importantly different wallpaper for each display monitor. Special extras with hot keys. Can automatically load pictures from flickr.
and secondly, my favorite
Manage wallpapers, display setting for each monitor, screensaver settings, and a very stable multi-display toolbar.
Also a nice feature is that windows can now easily trasfered to the next monitor (even if maximized) with a added button, located at the top of each window.