Directory of Expert Witnesses, Consultants, Etc. is a free online directory of 15,000+ experts, expert witnesses, investigators, court reporters, consultants, and litigation support professionals.
According to House of Butter:

The redesigned site features listings in 36 main categories, with over 2,300 searchable subcategories ranging from accident investigation to medical/health to document analysis. Users can browse by category or use powerful keyword searching to quickly zero in on the specific expertise or service they require. Many listings also feature links to ALM’s VerdictSearch(R), allowing users to view verdict details on cases the expert has testified in, with a single click.