Linaria maroccana, 'Licilia' Series, 'Licilia Azure'- available from Geo, also in mix,peach, rhythm & blues mix (red/violet). Very quick to flower. Blooms in 6 weeks for direct early spring sowing. 2 feet tall. Works well in large containers and bed drifts.
Linaria purpurea "Toadflax" - Tiny violet-blue snapdragon-like flowers over narrow, whorled, blue-grey leaves. Blooms all summer in full sun to part shade. Drought tolerant and reseeds. 3' high and 1' wide. Looks great in groupings. Native to southeastern Europe. Perennial zones 5-10.
A new plant variety on the market is Lunaria annua 'Corfu Blue'. Despite its name, this honesty is at least semi-perennial. It is in full flower now (March 2014) and is really appreciated by the small tortoiseshell butterflies. Lunaria 'Corfu Blue'