Bacopa (Sutera cordata). Trailing white flowers; June to frost. Perennial in zone H2.
Heliotrope. Scented, deep violet to white flowers come most of the year in warm areas; perennial in zones H1-H2.
Kangaroo paw (Anigozanthos). Deadhead the red, purple, green, or yellow blooms to keep them coming from spring through fall.
Nemesia caerulea 'Blue Bird'. Violet blue blossoms with yellow centers; perennial in zones 14-24, annual elsewhere.