Penzeys is nice and has lots of information on their website, but for a better deal check out Lonestar Culinary - Flores Spice Co., next to El Bolillo bakery, across from the farmers market on Airline.
Best Spice Shop Houston 2010 - Penzeys Spices
Just step inside this Heights shop and smell the difference. It's like taking a gourmet-shopping trip around the world. Want Vietnamese cinnamon? Tellicherry black peppercorns? Szechuan pepper salt? Mexican oregano? Yep, Penzeys has all that and more, offering spices, herbs, seasonings, gift boxes and some pretty cool pepper mills and saltshakers. It's a great place to buy gifts, and novices need not worry. The friendly staff will offer recipes and sniff tests. You could spend hours here just sniffing all the different kinds of chili powders. It's spice heaven.