If you're bored of the same old desktop wallpaper images, then Picture of the Day may be able to help. This simple tool connects directly to your choice of many popular "Picture of the Day" sites: everything from NASA and National Geographic, to animals, cartoons, and cute girls in bikinis. (Only "in" - no adult material.) Today's image is then downloaded and set as your wallpaper.
If you have a favourite "Picture of the Day" site that's not listed, then you can add it here. We pointed the program at Flickr's "interesting" URL - http://www.flickr.com/explore/interesting - and it correctly downloaded the main picture from the site. There's no great intelligence behind this, so for instance it won't download the image with the highest possible resolution, but if you choose your site carefully (or have a small screen) this really won't matter.
Click Settings and you'll find all kinds of useful options to change how the program works. For example, by default Picture of the Day will download new wallpaper every 8 hours, but you can change this to every few minutes, daily, weekly, monthly: whatever you like.
It's also possible to have the program use the pictures it downloads as a screensaver.
And if you're really just interested in photography, then you can turn off the wallpaper-changing functionality altogether, and just use Picture of the Day as an image collector. Give it the URLs of your favourite sites, it'll download new pictures every day and you can browse them all later.
The list of sites provided isn't great, but it's easy to add more, and overall this is a useful and well-designed way to spice up your desktop wallpaper