I use two different sites

I really like both of these. They have a wide range of variety and every seed I buy from them germinates.

http://seedrack.com/10.html

http://hirts-gardens.hostedbywebstore.com/Seeds/b/2260966011

Park Seed would be good too though, they just don't have as big of a variety. I know you have said before that they have good seed. I may buy some from them next year. I'm going to try to save some seeds from this year's crop for next year. There is a process to it though. I'll try it out.