While my shop is a bit bigger than a regular garage, we've started using Sears Edsal heavy duty shelving units. Depending on sale status, they run ~$75-$85/unit, and that's for the 24X48X72" units. I have started stacking them for extra height for the light stuff storage. I'll take three units, and make two tall ones out of them.
One thing I do is replace the cheesy particle board shelves with 3/8 plywood, cut-to-fit and painted white to reflect more light. They work great, are quite stable, and adjustable. They work great for tire racks, too, just replace the plywood with 2X4s screwed into the long sides.
Gene Beaird,
Pearland, Texas