Dave,
I guess "regional seeds" could be a misnomer. Instead of PNW, one could say "short season and cool climate areas". Maybe "large daylength variation".
Instead of "Southern", one could say "hot summer".
Instead of Northeast, "short season and cold winters"
But "PNW" is how I think of Ed Hume and Territorial, since they are local to the PNW and advertise that way. Ed Hume is kind of a NW "personality" and many of his awards and books are regional.
(GARDENING WITH ED HUME, NORTHWEST GARDENING MADE EASY. )
Territorial Seeds - "West of the Cascades" is the term they use
Ed Hume Seeds - short season and cool climate areas. ... high altitudes and early or late planting in warm climates.
Here's one company that advertises itself as specializing in a region:
Southern Exposure Seed Exchange - Mid-Atlantic and Southeast,
I'm not wedded to the idea for the Green Pages, but when I look at a new seed company, I always check out their "about" page to see where (and whether) they have a trial farm, and whether they claim to be particularly familiar with and stock seeds for my region.
Regional specialization could easily be stated in comments or reviews instead of check-boxes.
P.S. I think you've added really great features to this, and it's already the most usable and helpful "Recommended" feature I've seen online. Is it getting heavy usage already? It seems to be filling up with new data very rapidly.