I live in a small town in a rural area and we don't have much variety in plants in local shops. I've purchased herb plants through Ebay and have had very good luck with them. When the local shop has sold out of rosemary plants on the day they were delivered, Ebay is an option.

I remember caddying for my Dad one Saturday when I was a kid in Upper Michigan. He sliced the ball on one particular hole, and as I searched for it I wandered into this massive patch of Spearmint. Mmmmm...

I have purchased absurdly inexpensive young orchids on Ebay with much success.