I use a protein powder from http://www.unikeyhealth... that is made with brown rice and yellow pea. I love the smoothies I make with it, and they're very filling.

Whey Protein powder is pretty cheap and versatile. But avoid if you are vegan.

There are actually whey protein powders that don't have lactose (whey isolate instead of concentrate). That said, if you want to avoid animal products, pea protein is a good option: cheap and high quality protein. It can be a bit more chalky than whey though.

I'm not a vegan, but I've been investigating healthier protein options instead of soy. Gena Hemshaw recommends hemp protein. Has anyone tried it?

To add lots of protein to smoothies without changing the taste or texture, i use pasteurized egg white , like "All Whites" or similar. I believe that 1/3 of a cup gives you the protein of 2 eggs.
You could probably also use dried egg whites.