I'm in full garden mode right now, and I'm talking a lot about it over on MNN and a little bit about it here. I think that growing something is important for several reasons, but I also know that there are many people who don't have the time or the space to do a traditional vegetable garden.
I do think, however, that most people have the ability to grow one container of something. If you're trying to get the most bang for your buck, herbs are the way to go. Herbs cost very little to grow, yet are pretty expensive at the store. You usually buy an herb in a large bunch, and chances are you use what you need for a recipe and the rest ends up going bad before you need it again.
Growing your own will both save money and keep you from wasting money and food. It will make a huge difference in the taste of your food. It may even encourage you to try new dishes.
I found this very informative video series over on monkeysee.com that takes you one step at at time through creating an herb container gardening. The first video is here, and you'll have to go to the website to view the rest.