I found this list on another forum a few years ago and just cut and paste it to Word, so sorry for the crappy formatting
Secret seed cartel, excellent service, and extremely rare types of interesting and tasty tomatoes.
http://www.secret-seedcartel.com
Victory seeds has a paste tomato that grows to over 1 lb called Romeo, as well as other great and unusual ones.
http://www.victoryseeds.com
Sample seed shop: quantities of 10-15 seeds of an unbelievable selection for about $1.25 to $1.50 each, and you really only need one plant to succeed. Very high germination rates.
http://www.sampleseeds.com
Sandhill Preservation- great prices, no shipping charge if you purchase more than $10 there, huge selection, and many rare and unusual varieties. They grow out most of their own seeds rather than being a reseller.
http://www.sandhillpreservation.com
Marianna's seeds- very unusual varieties you just can't get anywhere else,a lot of crosses from Bill Jeffers,who is very well respected in the tomato breeding world.
https://www.mariannasheirloomseeds.com
Ohio heirloom seeds- they sell a large pink Russian heart that I adore called Rosovyi Myod ( pink honey) and many others, shipping is one low price, great service and selection.
http://www.ohioheirloomseeds.com
I HIGHLY recommend the Rosovyi Myod from Ohio Heirloom seeds. They will remind you why tomatoes are considered a fruit, rich vibrant flavor, sweet with a hint of tart and highly productive through drought and heat.
I have ordered from the Seed Cartel, Sandhill, Mariannas, and Ohio previously and would personally recommend them. The others I vouch for because the lady that recommended them has never steered me wrong