I was reading "The guys guide to geek girl" when I found one tip (of finding a single intelligent girl) I can personally testify as effective. The tip is to post intelligently in a forum or mailing list . Yes, it works. If you're insightful or consistent enough in your writing, people of all genders are bound to email you personally, especially if your view on an issue is very similar to theirs. Depending on the community, you will soon get email from one or two girls, hopefully single :-). But do remember that if you write better than most, some girls might treat you as if you're an old, untouchable guru. They will not initiate a close friendly discussion with you. If that happen, it is you the one who should initiate a personal communication. Of course if you're specifically interested in someone, you can zero in her posting by disputing or clarifying it. She will feel appreciated.
There is a science joke, which has been polished over time:
* A specialist knows more and more about less and less until eventually he knows everything about nothing.
* A generalist knows less and less about more and more until eventually he knows nothing about everything.
I consider myself a generalist thus I declared that I know nothing about everything.