Depending on what part of the country you're in, it can vary greatly.
I would start with the dandylion, as the whole plant is edible, from flower to root. My wife makes a wonderful dish from the flowers by putting them in boiling water for a few seconds (blanching) then transferring to them to cold water. After that, just saute them in a little salt and oil. Its a lot of work, but it's worth the effort. Most wild edibles, and game for that matter, will have a stronger taste than you expect, so a little goes a long way.

For a beginner, I would recommend getting a Peterson's Field Guide for your area. Its a great way to start building your foraging knowledge!

Both wild edibles and the study of herbology are important to us. If you care to follow us, I know we will get around to blogging it soon. We have plans for a separate perennial garden next season which will incorporate some of our favorite wild foods.