Benchmarks

Does anyone happen to know if there is an Internet site that does a real good job with benchmarks. I am thinking of buying a new computer and I would really like to see the speed comparisons and how the different ones stack up. A friend of mine bought a Performa years ago and when he got it, it ran about as fast as an old SE I had. It was really bad. Sometimes the Mhz does not tell all. Sometimes the dual processors don't give you much more than a single.