Zappos.com - Free Shipping and
Shoes from Shoebuy.com - Free Shipping & Return Shipping have good selections and there is no charge for shipping. You can order several pairs, then send back those you don't like for whatever reason, since they comp the return shipping as well.
I've ordered boots of the same style in three different sizes before and then just returned the two that didn't fit.
Other mail order (but you have to pay for shipping):
Hitchcock - Wide Shoes for Men - Mens Wide Shoes, Extra Wide Shoes, EEEE, Orthopedic Shoes (Hitchcock Shoes)
Men's and Women's brand name shoes available at bamason.com