If you're gearing up for a fall garden consider creating a planting yardstick from a 1.2m long, 10cm wide board. It'll help space out both your garden rows and the amount of space you need between each seedling.
Martha Stewart's weblog shares the simple design for the "yardstick" and points out an important piece of basic gardening advice -- seeds or seedlings are spaced according to their type; lettuce seeds can be planted every 15cm while tomatoes need 60cm between each seed or seedling. Cut alternating notches in your board every 15cm so you can easily measure the distance from seed to the next.
The spine of the yardstick also serves to mark your gardening row; if you cut a 45-angle bevel on the edge you can press the yardstick firmly into your soil to create a furrow for your seeds.
This yardstick may be too basic for experienced gardeners but if you're still growing your green thumb consider it a helpful aid.
Planter's Yardstick [Martha Stewart]