One of the traditional times to plant for optimum results is in the fall. The day temperatures are colling which makes it easier on the above ground parts of the plant and the soil is still warm, promoting good root growth before winter cold comes. All growth that plants make now to establish themselves will show up as vigorous spring growth and bloom. You get a jump ahead with that coming growth by planting now. Almost everything can be plantied now. Hardy trees, shrubs, perennials will show good results as they mature when planted now. (But do remember that planting from containers at ANY time is also quite acceptable since the growing plant will immediately begin to establish itself in your garden when planted from directly from containers.) Now is also a great time to select from nurseries since it has been a slower season than typical due to the economy. Often there will be a good selection and the plants are now bigger than typical for the container size in regular years. Wait to plant tender things until next spring when they will have a long growing season to establish themselves before cold comes.
There has been a lot of hybridizing effort with all kinds of plants. Annuals and perennials now come in a wide selection from the old favorites. Look for other colors, more flowers, compact habits, variegated leaf forms within your old favorite selections. You will often make surprising discoveries.
The same holds true for the larger plants…trees and shrubs. We are blessed with a mild growing climate and long growing season where many things flourish. You can pick your traditional favorites as well as try a few new things and sample some of the exotics.
With old stand-bys like roses, there are MANY selections outside the main groups of hybrid tea, English, and floribundas if you look. The carefree species and their hybrids as well as the older classes and the shrub rose groups yield surprises. Flowering shrubs now come in dwarfer sizes and heavier flowering forms in many cases. The hybridizing effort has addressed the landscape needs of smaller sized gardens as well as lower maintenance plantings. Water conservancy is also addressed if you choose from xeriscape / Mediterranean climate plants.
A visit to your local nursery may give you an idea of some of this.