My husband drystacked Austin Cream Limestone on a partially submerged footer of pea gravel. Mine was a 15X30 raised vegetable garden, and was the cheapest stone alternative we could find at the time. The Austin limestones are the cheapest stones we can get in the Houston area that are stackable. Google dry stacked stone wall, and you'll get a bunch of DIY hits.

We've got several large beds whose walls are those pavestones that they sell at Walmart and at Home Depot. They are less than two bucks apiece, easy to use, look good, stay in place---I'm very happy with them and intend to make one or two more beds...they are made with a lip that keeps them from shifting once in place. They are called Windsor stones, and they come in at least three colors.