Ironic, considering your name has Whitehat in it I'd also check out articles that you find on google that review some of the themes, here is one for example: http://www.creativebloq.com/web-design/free-wordpress-themes-712429 There are plenty of others but make sure to understand the sources that lead into the themes before taking any risks with themes.
I was going to suggest the CreativeBloq list as well. We've made our internal list that we've curated from multiple sources: The CreativeBloq list quoted above http://www.syntaxxx.com/free-wordpress-themes/ http://designscrazed.org/free-premium-wordpress-themes/ As you search for themes that are viable for your project, bookmark or make notes of other themes that you like, but that don't fit the current project. Use this "swipe file" later to speed up the search for a great theme for your next project. Just my 2 cents, that's he we do it for our projects.