I think it all depends on what age range you are comfortable with. If your platonic friends are mostly older, perhaps your ideal partner will be older too.

Something I keep hearing lately (from a Match.com commercial) is that more people are meeting through dating sites than any other way, these days. Not that you should or have to, but it is an option that can allow you to narrow your focus to people who share your open-minded attitude.

I am not sure exactly how open-minded you are talking about but the range runs from okcupid.com which is a simple, free dating site to adultfriendfinder.com which specializes in specifically sexual match-ups of one kind or another and even polymatchmaker.com which obviously focuses on people interested in non-monogamous relationships.

Those are just three, there are TONS more out there. You can narrow your focus religiously at Catholic or Jewish sites or politically at match making sites for Democrats... the possibilities are probably endless.