As far as annual flowers go, marigolds offer one of the best bangs for the buck. After you put them in the ground, you can leave them alone and they'll bloom until fall. Hardy and forgiving, marigolds tolerate most any soil condition and will even rebound after being nicked by the lawnmower. The plants can reseed themselves, so depending on your location, you may find marigolds popping up next spring. If you're so lucky, dig them up and move them as you see fit to enjoy them for another season. Available from Burpee; $3.95 for 50 seeds.