I like to let the kids make their own orange juice once or twice a week (it's actually made with clementines not oranges, but we call it orange juice anyway). It's a great Montessori motor-skills exercise with cutting, squeezing, and pouring practice. It is also useful for being able to describe the sequence of events (they tell me what we do first, what comes next, etc..).
Here are some pictures of the kids making their own juice:
In the past, we would also include a lengthy first step that involved scrubbing the clementines and then rinsing them in water, which the girls loved to do. Unfortunately, my husband decided that the wonderful fruit-and-vegetable-scrubbers we had would be great for cleaning the bathroom, so we've stopped that part until I can get some replacement scrubbers.