As I was "stumbling"* around the web today, I came upon this page which is quite clever and very accurate. Hope you think so, too . . . .
*Actually, "stumbling" is an accurate term if you're not familiar with it. It's a Firefox browser extension that lets you pick search options based on your interests and fetches pages that people find useful. It has been a very good tool to find new viewpoints on topics that interest me. Here is where to go to install it.