Plumbago (or Leadwort) is one of the Perennial plants I wish I had found sooner.  It has beautiful sky-blue or white flowers that very much resemble phlox.  It blooms intermittently through the summer, but profusely in late summer and fall.  It's shiny green leaves form a graceful shrubby mound, but it can also be pruned to  to spill over a wall or up a support. 

Plumbago is a native of South Africa and likes a light, sandy soil with good drainage.  It will do well either in full sun or partial shade, but flowering will not be as profuse in the shade. Plumbago can be pruned into a formal or informal hedge, and it's graceful arching habit makes an attractive but rather tall ground cover in the more temperate zones.  It can also be considered for use in shade gardens, rock gardens, container gardens, or as a mid-border plant.  It blooms past the first light frosts, and the leaves turn a rich red as the weather turns colder.  Plumbago also makes a nice addition to the habitat or wildlife garden, and butterflies love it. 

Plumbago loses it's leaves in the winter and is rather late to come back the next spring, so be careful when cultivating the areas where it grew last year.  It is supposedly hardy to Zone 5, but should be heavily mulched or brought indoors in harsh winter areas.  It can reach 8 feet or more in temperate areas, and as such can be used as a flowering climber in certain places.  It can be propagated by seed, division, or cuttings taken in winter or early spring (you can really take cuttings anytime, but once buds are set, you will lose some bloom if you do it during the summer).  It blooms off the current season's growth, so this worry is eliminated if cuttings are taken during the winter.  Anyhow, once it is up sufficiently in the spring, cut it back so that it will produce new branches and thus, more blooms.   

Plumbago looks good in the garden when planted with Black-Eyed Susans, Red Chrysanthemums, Purple Coneflower, and Asters, to name just a few.  It also has some merit where deer are a problem, as the deer will only eat it if pressed for other food sources.