Yes, there is. I do not know much about them but I have seen and heard about the software used for them. I wish I could be of more help. Hopefully some other members or membi could help you
One of the best search engine scripts i have used is phpdig. It is free search engine software that allows websites to be submitted to the search. You then select this website and a bot will run from your computer and index the websites. I can take a long amount of time unless you are happy to leave it running all the time or use more than one computer.
There are actually tons of search engines. You would either need to use an existing script, or hire someone to write one. You could also just do what ninja.com is doing, and use Google search and make money off it
if you are going to start a search engine then you are better off just using google like fewleftstanding mentioned above. That way you dont need to index the websites yourself which saves you a lot in server costs and you get paid for people searching. There is a reason people say "Google it", its cause thats what most people want to use to search and most people dont like change.