While searching for layout ideas for my garden, I came across a free online garden planner. This version is easy to use and you can print out a copy of your garden, but it doesn't allow you to save it.
You can also buy and download a complete software version at Garden Planner for $19.95, not such a bad price considering you can use it for vegetable or ornamental gardens.
They have sample layouts or you can create your own space, free form style. It was fun to pretend I had planted a much fancier garden than I actually did!