Tasty Planner is a one-stop meal solution. At this site you can find recipes (including ingredients, prep time and cooking instructions), share recipes, build a personal recipe box, plan any number of meals and - the best part - generate a grocery list.

When you build your weekly planner of meals, you can automatically generate a list of items you'll need. You can reorder the list, check off items you already have and add your own items. Grocery lists can also be integrated into iPhones, or printed the old-fashioned way.
For Mac OS X users can download a dashboard widget.