Jojo, a great smoothie from someone on this website -- I don't remember who, but I thank them! -- has been a staple for me when I couldn't eat much. And it tastes delicious! Here are the ingredients:

1 Ensure or Boost
1/2 c. oatmeal
1/2 c. vanilla yogurt
one frozen banana (broken into pieces and frozen in plastic bag)
1/4 c. milk
1 scoop protein powder (vanilla is best)

Blend really well -- that way the oatmeal won't be gritty. It makes two LARGE glasses-full, so a complete meal's-worth, at least.

Enjoy.