Arthur's Free Flower Clip art: Over 300 clipart images.
Clipart ETC: Flower & Shrub Illustrations: Over 3040 clipart illustrations of flowers & shrubs.
Flowers by Inges - A large collection (over 1000) of nice clipart graphics of flowers.
Free Flower Clipart by fg-a.com: Asters, Aztec Lily, Chinaros, Crocus, Poinsettia, Bird of Paradise, Lilies, Red Poppies, Azaleas, Blue Bonnets, Chrysanthemums (mums), Dahlia, and several other flowers and flowering plants.
Free Flowers Clipart at freeclipartnow.com: Bouquets and Baskets - Roses - Sunflowers - Tulips - Other Specific Flowers
Free Clipart of Flowers by webweaver.nu
The images below are from a wonderful Web site called Reusable Art - Click on the images to see a larger version.
Related: A Flower Book by Eden Coybee and Nellie Benson