Herbs -- Dill, basil and sage are the ones we use most, and I have saved a ton of $$ growing them instead of buying them. Rosemary too, though depending on where you are, maybe not. Here in zone 4 rosemary is pretty much a harvest-and-dry end-of-season herb.
Veggies -- lettuce! Tomatoes, peppers, squash, beans and some sort of root veggie (beets, carrots, etc). Zucchini is great for a first timer, it's pretty much guarenteed to grow *anywhere*.
Fruit -- Watermelon -- though it should go in a patch that has a TON of room, watermelon vines take up a lot of space. Also watermelon is better grown in a warmer zone. Strawberries and raspberries and/or blackberries are also good. Apples. Be warned, most berries/fruit require a lot of patience and multiple growing seasons before you get a harvest. Our raspberries are on year two and we're going to literally harvest about a dozen berries this year. But *next* year, LOOK OUT, we have SO MANY raspberry vines growing this summer that we'll be up to our necks in berries next summer. On the other hand, I only got about a dozen strawberries from our new patch last year, but THIS year, the june bearers gave lots of berries, almost 32oz as of this writing. And the everbearers haven't even started to flower yet, so we'll get another crop in a couple months. And we have a small patch designed for 2 adults.
HTH,
Whitewater