If you own the property and there are no hoa rules, post a sign saying no parking private property. Out line your property with red or yellow paint like they do in the cities, and on the sign make it clear that the car will be towed at the owners expense, and any damage caused to the car being removed will as well be the problem of the owner.
As to dogs, what are the leash laws, if you have a neighbor using your lawn as a toilet, set up a vidcam and then sue in small claims. Or just find a farmer get a truck load of manure and dump it in his driveway, massive turnabout is fair play especially if you have proof of a**hole behavior.
The best solution I've heard of for other dogs crapping in your front yard is to douse the "gifts" with bacon grease. The offender will then return and eat the offense (because that's what dogs do - they can't resist bacon!). Bwahahahaha!