VA_LongBean
Deeply Rooted
Pinetree Seeds, Baker Creek, Southern Exposure Seed Exchange, Seed Savers Exchange, and trades.
I have two sites that are good for 'sample-sized' seed packets. One is TradeWindsFruit.com, a real favorite of mine and the other is La Jardin du Gormet.Excellent sources already mentioned; I'm going to add The Sample Seed Shop http://www.sampleseeds.com/