Honestly (not speaking from my experience, but from my sister's) I think sites that are not specifically for dating are best at meeting a variety of people. I mean, if you must do it via online, being active on sites like FB and sites where you have conversation going (forums with people near your area or not depending on if location matters to you) are amazing for meeting people. I've been involved in a few different forums. Here, a coffee shop for writers, prisoner pen-pal forum, and a support group forum. Those are all things I'm involved in (well, not willingly involved in the problems I have which caused me to seek a support group). But I'm involved with 2 prisoners who I frequently conversate with. Not romantically though. They're just lady friends. I'm a writer, so the writer's forum is a place I can really always have something to say and can relate to others.
So being involved in something like a forum that's kind of aimed for something you do (a hobby? reading, writing?) will bring you to definitely having conversations with others who are doing/enjoying or suffering from the same things. It's an easy way to have conversations with tons of diff. people.
I have never used a dating site though. If I were looking to date though, I'd just be more aware of others I see when I'm at places I enjoy like the book store. If I were looking for a date, I'd just be sure to strike conversations with people there or somewhere else I frequent for enjoyment. You'll have something to get the ball rolling and likely have things in common.
Sorry that I don't have site recommendations, but maybe these suggestions might be of help? Reach out to different people on FB. There's a non-profit organization group I work with and when we want to reach out to more people online, we look for certain terms/phrases to search them out and that's how we find like-minded people. Keep an eye on people who share the same likes, dislikes, etc. Commenting here and there on something they say that strikes you (good or bad) will bring up conversation. I've met TONS of friends on FB just by this.