Gardener's Supply Company provides a free online planner for you to use when planning your garden beds.
Most of the online planners that I have come across require an annual fee. This planner is ideal for the square foot gardener too. For more info click here for the Gardener's Supply Company planner.You can save your plans and the company even provides planting instructions for actual planting.
If that is not your cup of tea, you can always create your own plan on powerpoint, and reuse the template year after year.