http://www.online4love.com is the primary way my husband and I meet likeminded "friends with benefits." There's no uncomfortable wondering if you ought to approach someone, you already know upfront when you meet them, and it is definitely worth the extra cost of becoming silver/gold imo, so you can exchange notes or pics before meeting and make sure its a good fit.
My hubby is str8 and I am bi and we have had no problem finding partners on online4love.com. We've had fun sex with lots of single men, single women and full swap couples that we met on O4L. And yes, I'm real, and no, I don't work for O4L or think they're perfect (they can be pricey and they goober up email sometimes,) but I think they're the best thing going by far for meeting other people who just want to have sex without strings!
For those complaining about the cost—ok, I agree, but I think you get what you pay for. I pretty much don't write people unless I can see what they look like and all, not because I'm shallow or a snob but because I want to know THEY'RE for real too and don't trust blank profiles...can you blame me? Also, it can be risky to contact people to swing with! Are they my boss? My brother? Twice my age? You get my drift. I’d like to know who I’m initiating a conversation with! The extra cost put into a good profile helps narrow down those you want to meet. How long do you pause on a profile that does not show a picture? (Faces can always be “smudged” until you know each other better to avoid embarrassing compromises.) And, although we are admittedly "just after recreational sex", part of having fun is that we have to LIKE our bedpartners too, so we look for things like a sense of humor and easygoing fun nature and a “click”. (And more expensive memberships include more matching criteria and stuff, too to help the odds of getting that “click” without too much searching.) So I guess I'm saying that if you don't cough up the extra cash for a full membership, don't expect overwhelming responses. There are lots of people who post their pictures and info, so when looking for people it's easy to breeze by the ones that don't. We may miss out on meeting some great people because of it...but we meet lots of great people too.
I agree there’s a high ratio of men to women, but I don’t know why that surprises anyone. Seems expected to me—although many women love sex, there do seem to be a lot more guys that are ok with swinging or casual sex than girls, for whatever reasons, and that’s not specific to O4L.
I definitely vote that it is worth the time and the money! We've had many a fun night of frolic thanks to connections we made on O4L. :)