I love the assortment of colors and sizes available for zinnias.
I usually can find Magellan, Zahara and Profusion zinnias at a nursery. If you want to grow these varieties from seed, I found them on the Park Seed website.
The following variety is and will grow up to 2 feet tall:
Thumbelina – this variety will reach up to 16 inches tall and comes in shades of white, yellow, orange, pink and red.
These varieties are medium sized in height and will grow up to 3 feet tall:
Cactus – this blend has rolled petals in shades of pink, white, red, orange and yellow.
Cut and Come Again – while the flowers are only 2 1/2 inches, they make up for it with beautiful yellow middles and petals in shades of pink, rose, magenta, scarlet, orange, yellow or cream.
These zinnias are considered giants as they will reach up to 4 feet tall:
California Giants – this blend comes in red, pink, purple or white
Benary’s Giant – the flowers are about 6 inches across and come in, white, red, orange, purple, pink, salmon or yellow.
These varieties are too cool not to highlight. They have multi colored petals:
Peppermint – the flowers are scarlet, crimson, orange, pink or cream with red streaks.
Queen Lime Red – this zinnia has red centers and the petals are shades of ruby with apple green highlights.
Queen Lime Blush – this zinnia has red centers and the petals are lime green with red highlights.
For zinnias, I would take a look at Botanical Interests, Baker Creek and Park Seed.
I recently reviewed seed ideas for calendula.