There is a lot of information to be found about herbs and spices. Here are some websites with useful, or at least interesting, information:
Gernot Katzer’s Spice Pages features extensive botanical and etymological information about spices, including the chemicals that give spices their flavours, and the names of spices in different languages.
Wikipedia of course has a list with information about herbs and spices.
And here are some links to spice mix recipes from About.com.