JurisPro is a free expert witness directory with an amazing amount of information. As opposed to other expert sites, here you can review the expert’s C.V. (in PDF format), see a photo, hear the expert speak, read their articles, and learn more about the expert’s background. You may search by keyword, or browse the list of expert categories, which is pretty extensive — even more amazing are the subcategories! I don’t know if the featured experts are worth your money, but this site is definitely worth your attention.