Here's a handy bit of freeware. WebDesktop lets you use any web page as your desktop picture. Simply enter the URL of a terrific website (like, say, this one), set the transparency and reload rate and you're all set! When in the background, the page you're monitoring acts as your desktop picture, but when in front, you can scroll, click and otherwise interact with that site as if you were using a typical browser.
MacDesktop requires Mac OS 10.3.9 or higher, is free, and universal.