My newly developed theory is that seeds from plants grown in areas similar to my own climate might be best adapted to my own garden, especially when they are open pollinated or heirloom seeds. Same goes for plants and trees.
Also, I've decided to try to stay within as near my geological area so my packages are not being shipped from ridiculous distances.
As a result, for myself I've given up on many sources located on the Pacific coast and far midwest that I've considered in the past (Territorial, Nichols Garden Seeds, and Seeds of Change used to be my faves). Just an idea.
That said, my primary sources this spring has been Johnny's Selected Seeds, Southern Exposure Seed Exchange, and Scheeper's Kitchen Garden Seeds. I also get seeds from Burpee that are sold in local garden centers. There's a tomato and pepper seed source in NJ that escapes me at the moment too.