Spice Ace is like a petting zoo for those interested in studying flavor. Each of their spice blends, chili powders, and salts have a sample container from which you can sniff or taste with a spoon. I had a fun time comparing Thai, Malaysian, and Singapore Curry Powders.
The fragrance of spices seemed to best what I typically buy in bulk from Rainbow, and the prices are reasonable (~$4-$12) considering you get a glass jar with each purchase.
1821 Steiner St, San Francisco, CA 94115