DCM, here is an idea. Go to your local craft store and find yourself a block of foam rubber that is about 4" thick, about 10" in height and about 6 feet long. Now, stop by another section of the craft store and pick up some twine or thin rope. What you are going to do is to go in about a foot on each end and push the rope through the foam rubber going through the 10" of foam (running the rope up and down inside foam). Leave yourself about 6 feet of rope hanging out the top. Once you have the rope inside the foam, go out to the garage and hang the foam from the ceiling such that the foam will hang about 2-3 feet off of the floor. TADA!!!!!!!! now, when you open up the doors, the foam rubber will cushion the one door as it comes close to touching the other door. As you walk by, you push the foam out of the way.
If your garage door comes too far back into the garage, you can do the same thing cutting two pieces of 1/2" plywood into 12x12" squares. Then, get your hands on some 1/8" steel rod. Drill an 1/8" hole through the plywood and push the rod into the hole (rod will hold itself in the hole due to friction, so, may need to use a drill bit that is slightly less than 1/8" to make sure you get a nice tight fit). Then you push the foam rubber on to the metal rods. If you open the doors up, the thin metal rods will flex and allow the foam rubber to remain between the two doors and worst case, you move the foam rubber back and forth between the cars to keep the foam rubber fairly close to a vehicle at all times to make it easy to walk by.