I do web marketing for a living and I can't say there's any one single site that's going to bring in the traffic you want. Try to think of web marketing like fishing, you want to cast a big net to catch the most fish.
You will have those sites that bring in more than others but that's going to be different from client to client. Marketing is adaptive. You try an avenue, gauge your success, change your methods accordingly, and explore other avenues.