My dog Timber used to be like that too. Sometimes she still gets a kick out of it.

There is a special type of collar (I can't remember what it's called) that, when the dog pulls on the leash, emits a high-pitched whistle. It confuses and surprises the dog. He might associate the scary whistling with pulling the leash and won't try to jump over to greet another dog. However some dogs may ignore the whistle and find the dogs more fascinating.

I agree, get some obedience training. It's worth it.