I absolutely love Renee's Garden Seeds (used to be Shepherd's Garden Seeds). She goes to Europe each year and tastes varieties from street markets. There, if it doesn't taste good and have unique appearance, you may as well not bother taking it to market, especially in France and Italy. So her selections are terrific. They're not designed to travel hundreds of miles unripe in trucks, like in the U.S. My kids have loved eating things like striped beets, pastel "sweet" radishes, purple tomatoes and tricolored matchstick beans! Especially when the flavor is sublime.

The garden center on the NW side west of Michigan Road on 71st Street that used to be called Scott's carries many of her seeds, and they have lovely plants as well--some are her varieties. They're not the cheapest but not terribly expensive either, and you will truly be serving the same vegetables that award-winning chefs across the world use.

My absolute favorite place to buy vegetable seeds is Pinetree Garden at www.superseeds.com/ . We've been dealing with them for years, and not been disappointed. Their unique feature is price. You get less seeds per packet (and do we really need 6,000 lettuce seeds every year?) and a typical packet of seeds is about .95 to 1.25. This allows me to do a lot more experimentation! You can buy larger quantities of seed packets, also well priced.
Another good source is Totally Tomatoes. Their catalog is kind of porn for tomato lovers, but they also have other vegetable seeds. I've had excellent luck ordering from them as well: http://www.totallytomato.com/
Enjoy your garden this year!