Save these fruits and vegetables for smoothies
Rhubarb
Figs
Eggplant
Bananas
Berries

Difficult to juice, but you can try (if you must)
Mangos
Avocado
Winter Squash
Papaya
Peaches

Add these to your compost bin or trash can:
Citrus rinds
Pits, including those from avocados, peaches, etc.
Apple seeds
Papaya peels
Carrot greens

Constantly updated, please feel free to comment~