Fruit juices are yummy (always fresh squeezed from your juicer...) and they're good in the AM. Veggie juices are kind of yummy (sometimes not...) and they're really filling and full of nutrients (good for lunch or dinner).
Pineapples, apples, pears and oranges are great to use, so is Watermelon and kiwi. Grapes too! And of course lemons.
Veggie juicing - try carrot ginger juice, that's yummy. There are also lots of green juices - add a few carrots, some celery, some cucumbers, some cabbage, and some herbs if you're adventurous. Dill tastes good in juices, so does cilantro.
When you get strong, you can add a bit of garlic and/or onion types - leeks, scallions, and onions. Also strong greens like kale and beet greens. These will make your juice taste less yummy, so be prepared.
Carrots and beets are both good for you and have sugar, so they can sweeten bitter juices. Get a book or take one out of the library, maybe, cause when you just start throwing vegetables together sometimes you get screwed.
And of course, if there are any specific ailiments you have, many different foods have different nutrients that can help you with certain things. But when it comes to taste...