I needed some rare earth magnets for a project and found this site from a google search. The information on here is completely exhaustive and the magnets I got were perfect for what I needed. Their calculator allowed me to figure out what strength would work right and their prices were good (although shipping was a little high.)
If I had gone with my original plan of buying something from Ebay, I would have ended up with magnets that were *way* too strong and wouldn't have worked well. The information on K&J helped me make an informed decision and get the right product. I appreciate that they only do one thing - magnets - and have so much background to help you figure out what you need.