A dish without spices is like a movie without sound. Spices come from every corner of the world and can be found in powdered form or seeds or even leaves. Overall spices will have better flavor and a longer shelf life if you buy them as berries or seeds and grind them just before you use them. Some flavors and aromas are even further enhanced if the spice is toasted in a pan over low heat for a minute or so.
Here is a list of sites that offer great spice information:
The Worldwide Gourmet
UCLA Medicinal Property of Spices
These lovely wooden signs Read-Think-Breathe and the lovely spice print are the work of William Dohman who sells them through his Etsy store.