I've personally used Plenty of Fish (briefly) and OKCupid (started using same time as PoF and still use it). I've found some interesting guys on there, kept in contact with a small handful , but only made it face-to-face meeting with one so far, which didn't work out. I'll hopefully be meeting another sometime soon.
Most Helpful Guy
As a girl, if you're willing to upload a fairly detailed profile and go through the large number of messages you'll get, you'll quite easily find some high-quality guys.1