Native Gardenias will flower in shade and they have a lovely scent as well. Ajuga loves shade and is a low growing groundcover that has a blue flower in spring I recall. I believe there is also a native Ajuga.
Eupatorium megalophyllum, also known as giant ageratum is an exotic but loves the shade and has huge purple flowers in Spring. It is dead easy to grow. Eranthemum will grow in shade and flowers for quite a while in spring.
