Fall is also the time to scatter seeds of native beauties like California Poppy. And there are plenty of cool-season vegetables to plant now.
Tropicals and Citrus are best planted in warmer months, though you can still sneak in a few before winter hits. Drought-tolerant trees and shrubs grow more quickly and are much happier when planted in mid to late Fall. So get out there and plant that tree you've been wanting to shade the house or patio! California natives also respond well to January planting.
On a budget? Buy Sages, Lavender or Rosemary in small and inexpensive 4" or 1 gallon pots to plant now, and they will take off quickly in Spring, often catching up with their 5-gallon-size cousins!