There's no reason to keep your cutting boards all stacked up together under the sink, constantly falling over when you move the bottle that's propping them up. Head to your local office supply store and snag a file folder rack. They're usually wide enough to keep your chopping boards organised without scratching them, and small enough to fit on the countertop or under the sink.
This is one of those organising tips that you have to see in action to really understand. You have to make sure the folder rack you pick up has slots large enough for your cutting board, and that isn't so flimsy it'll just tip over when you put a board or two into it, but if you find one like the one pictured here, you won't have a problem. It'll definitely take up a bit more space than just stacking them up against the wall of your cabinet, but it makes them much easier to reach, store and even dry after cleaning.
17 Ingenious Things to Do with Old Office and Kitchen Supplies [Quick and Simple via Tipnut]