Every year it gets more difficult to separate Web wheat from chaff and pick a handful of sites out of billions to receive the Scientific American.com Science and Technology Web Awards. The Web is no longer just a tool for finding the occasional fact or trivium--it's a necessity, an integral part of our daily lives, and the sheer amount of information available can be overwhelming. But somehow, once again, we have winnowed the best sites from the rest. We think you'll agree that the 50 science and technology sites listed here are indeed worthy of high praise.

2004 will go down in history as the year the rovers Spirit and Opportunity landed on Mars, the year the Cassini-Huygens spacecraft entered Saturn's orbit, the election year in which the issue of stem cell research loomed large, and the year predicted to contain the costliest hurricane season ever recorded in the U.S. In addition to the best sites documenting these milestones, you'll find among our award winners Web wonders commemorating complicated figures like Einstein and A-bomb creator Robert Oppenheimer. String theory, the ancient Olympic Games and evolution also get their due. We're pretty excited about these selections and think you will be too. Did we miss one? Nominate it for next year. Just send us the url.