I wouldn't recommend using email harvesting programs, because if your not careful you can be classified as a spammer and get booted from your host. But as long as you understand the risks and are careful you could give "gee whiz" a try. It will search all the major engines with the keywords you specify and the bring you back the email addresses.
Email harvesting programs generally have spiders that crawl the sites and capture any email addresses that they find. (There's two ways that I've seen these programs find the sites - #1 - they crawl the results of a specified search on search engines. #2 you start them out with your chosen keywords and a site and they just follow every link they find and take email address from pages that they find relevant to the keywords you tell them)