Before I got into grounding myself I did a significant amount of home repair including helping a friend properly ground his very old house's electrical system. We dug a small trench about 6" deep, 8" wide and 5' long in order to properly ground his house. We drove approximately 5' lengths of rebar (available at home depot) deep into the ground and then used an extra piece so that the top of the rebar was about 6" below the typical surface of the yard. Using clamps and some very heavy wire we connected each section of rebar to the next so that there was essentially a line of rebar connected by copper wire spaced out heading away from his house with the closest piece of rebar being very close to the house and under his electrical panel. After backfilling and letting the grass grow there is no danger of running anything over with a lawnmower, there is just a heavily insulated wire that comes up from the ground right next to the foundation of the house and attaches to the rest of the panel.
This has worked for him for several years and is how I intend to make my own grounding rod when I live in a house again.