I've discovered a great source of most spices at prices significantly less that what your supermarket charges: The Spice Barn.
The Spice Barn was recommended to me when I started making my own sausage and needed spices and seasonings in larger quantities. They offer spices in containers ranging from a small table-top shaker up to about 50 pounds. - all for a lot less than you are paying at the grocery store.
I started keeping track of the spices and seasonings I use frequently, and then purchase a year's worth of each at a time.