We have done a lot of socializing with Bailey at the dog park and obedience. She too was doing the humping/jumping on top of other dogs thing. However, she has learned her lesson about who she can do that with and who she can't. It only took a couple of dogs to "tell her off" for humping/jumping on them for her to stop.

She currently does the jumping on top thing with Guinness, but in that case, we correct her, because Guinness is rather submissive and he won't "tell her off". All we have to do is give her a warning and if she doesn't listen, we spray her on one of her hind legs with water from a spray bottle. That usually does the trick.

I agree with Kfamr and wolfq about socializing and obedience. Good luck!