From the ArcaMax Publishing, Gardening Newsletter:
http://www.arcamax.com/news/gardening/s-156706-316914
Question: Can I conceivably fit broccoli, brussels sprouts, carrots,
radishes, kale, snap peas, beans, cucumbers, peppers, yellow squash,
tomatoes, and cantaloupe into a 4' x 8' raised bed?
Answer: If you plan the garden out carefully on graph paper, you'll
have your answer. Some of your crops can be grown in succession: for
instance, since peas don't thrive in summer heat, you can follow them
with a quick summer crop like cukes or squash, and grow them up the
pea trellis. Growing vertically is a great way to expand your space,
so put fence or trellis up on the north and west sides of your garden
(a shorter one on the west side so it won't create too much afternoon
shade). Dense plantings will compete more, so enrich the soil with
compost between plantings, and make sure everything gets plenty of
moisture.