This is what we did when our doberman was a puppy. I didn't knee him hard or anything, but every time he'd jump up, I'd hold my knee up and basically let him run into it. only took a few times and he quit.

With other folks' dogs, I'd do the "turn your back to them" thing. Whether they were jumping up or just being pushy in general, or even a dog that seemed to be potentially a little too aggressive, I'd just cross my arms and turn around and they'd almost always calm down immediately.