I like pinetree garden seeds. www.superseeds.com
I have a table full of seed catalogs. it's the only part of this time of the year that I really enjoy. Hot tea, a couch, a wood stove, and a table full of seed catalogs.
I like Territorial Seed Co. http://www.territorialseed.com/
Am trying to find more resources for heirloom seeds though, so I'll stay tuned to this thread to see where other folks go.
Baker Creek Heirloom Seeds - http://rareseeds.com - has the best catalog that I've seen. It's a work of art in itself! Haven't ordered from them as I just got the catalog about a week ago.