There are a whole bunch of websites that try to help parents pick out the safest car seats. The book "Raising Baby Green" By Alan Greene indicates that the organization with the strictest safety standards is the Consumers Union (consumerreports.org). Unfortunately this website requires a subscription so its not easily accessible to everyone. The book says that the Consumers Union uses higher speeds and tests both front and side collisions, and thus has better results than some of the other companies. The two car seats that performed the best were: The Baby Trend Flex-Loc and the Graco SnugRide with EPS. As it turns out, the February 2007 crash-test results were withdrawn because they appear to have been performed at speeds higher than intended (70mph instead of 38), however I figure that if the seats safe at 70mph its probably safe at 38mph. I'm looking forward to this years test results.
So far I have found that the Graco SnugRide is easier to locate in stores, but you have to read the fine print to find out if it has the EPS foam or not (all 2007 models have it). Plus, it comes is a very wide variety of fabrics. I've read some regular consumer reviews and most people seem very happy with it. I think its on the heavier side for an infant carrier but if its a matter of safety a few extra pounds are acceptable in my book. If you have any other information about car seats, I would love to hear it.