Lysimachia punctata - more commonly known as Yellow Loosestrife this plant is ideal for full sun and half shady areas, they flower massively during summer with clear golden flowers enhanced by bright green foliage on the flower stalks. Lysimacha is suitable for moist spots particularly suited to the side of a pond they spread slowly into larger clumps. This herbaceous perennial grows up to 3' tall in zones 4-8.
Summersweet (Clethra alnifolia) 'Hummingbird' --- fragrant white flower spikes attract butterflies. Compact habit makes it good for small gardens. Effective in mass, mixed into perennial borders or along foundations. Grows well in wet areas.
Heucheras are more or less evergreen, clump-forming herbaceous perennials. Heuchera micrantha 'Plum Pudding' is a particular favourite of mine and my clients. It forms a compact clump of lobed, deep beetroot-purple dusted with silvery-grey leaves and slender stems to 60cm bearing insignificant white flowers. It requires a position in full sun or partial shade in moist but well-drained soil where it will make a height & spread of 0.1-0.5cm in two to five years.