Hi Mary,
Its a good time to be an adventurous gardener. The Internet offers access to a lot of seeds and other resources that were very hard to find a few years ago. A few places you might look (there are many others as well) for unusual seed varieties:
Chiltern Seeds
http://www.chilternseeds.co.uk
British based company with very large selection of vegetable seeds
Evergreen Seeds
http://www.evergreenseeds.com/vegetableseeds.html
250 varieties of Asian vegetable seeds and
books for Oriental
gardening and cooking
Johnny's Selected Seeds
http://www.johnnyseeds.com/
large selection of organic and non-organic vegetable seeds especially for cooler climates; garden supplies and informative catalog
Kitazawa Seed Company
http://www.kitazawaseed.com/
US company specializing in Asian vegetable seeds
Nichols Garden Nursery
http://www.nicholsgardennursery.com
family owned source of seed for many unusual leaf vegetables
Peaceful Valley Farm Supply
http://www.groworganic.com/
very large selection of organic seeds and supplies including good range of cover crop seeds and agricultural tools, geared toward organic farms and larger gardens
Sakata Seeds
http://www.sakata.com/
Japanese seed company with distributors throughout the world
Seeds of India
www.seedsofindia.com
US company specializing in vegetable seeds of the Indian sub-continent
Terroir Seeds
http://www.underwoodgardens.com
specializing in heirloom vegetable seed
Thompson & Morgan Seeds
http://www.thompson-morgan.com
British company with huge selection of vegetable seeds
VNR Seeds
http://www.vnrseeds.com/
Indian vegetable seed company with branches around the world
You might also check in
Eric Toensmeier's book Perennial Vegetables