If you're an astronomy nerd you likely already know about the Astronomy Picture of the Day, a Web page run by NASA that displays a different astronomy-related image with a brief explanation every day. APOD Wallpaper places the picture of the day on your desktop and automatically updates it daily, making sure that you don't miss out on any space-related geekery.
The program appears as an icon in the system tray once it's opened, and clicking on it gives access to a menu with a handful of settings. You can set whether the image will be stretched, scaled, centered, or tiled, and whether the program runs on start-up. The program can be set to update the image at a particular time each day, or the image can be updated manually. Using APOD Wallpaper doesn't mean that you have to miss out on NASA's explanation of each image, either; right-clicking on the icon reveals a context menu item that provides the explanation in a small pop-up. There's no Help file, but everything about this tool is pretty intuitive. Overall, APOD Wallpaper is a simple program, but it's a lot of fun to have around if you're as fascinated by outer space as we are. It's nice to look at and educational, too.
APOD Wallpaper comes as a ZIP file and is accessible after extraction with no need for installation.