This is very cool! Yeah, doing it by hand might not be ideal, but I think you'll probably want to review the submissions anyway. Another thing you can do is maybe setup Amazon Turk to have Turkers verify, but that will cost money, of course.
There are lots of ways I could find the companies by scraping websites, which would be quicker in the long run, but many sites are not amenable to scraping. For example VC firms always list their portfolio companies but sometimes they only have graphics of their logos, without textual names or links.