All Things Iris
Sells Pacific Coast, Siberian, Japanese, Spuria, Species, and Tall Bearded Iris.
http://www.allthingsiris.com/

Argyle Acres
Specializes in Texas hardy, bearded irises, and antique plants.
http://www.argyleacres.com/

Bianco Iride
Italian iris hybridizer and grower offers bearded and Siberian varieties, as well as some daylilies. Ships worldwide, but not to North America.
http://www.biancoiride.it/

Blue Bird Haven Iris Garden
Iris nursery in California, providing mostly tall bearded varieties. Online product listing and order form. Also summary information about the Victorian show garden on the nursery premises.
http://www.bluebirdhavenirisgarden.com/

Blue J Iris
Specialist nursery in Nebraska, offering a large assortment of bearded irises, emphasizing rebloomers, space age types, and other specialties. Illustrated online catalog.
http://www.bluejiris.com/

Cayeux
Company in France offering online sales of tall, intermediate, and small bearded irises, as well as iris publications.
http://www.iris-cayeux.com/