That myth of how vegetarians can't get protein is nicely addressed here in a post from Mind Body Green and ultra-marathoner and vegan, Rich Roll.
Quinoa, tempeh, seitan, beans, and lentils are some of my favorite foods, but Roll's post makes me want to get in on that spirulina game.

I'll never be anywhere near the shape that this dude is in, but i do try to eat as health-consciously as i can (in between trips to gorge myself on sandwiches from Blackbird Pizzeria, which have a nice amount of protein-rich seitan).

My experience with non-vegetarians questioning my health always cracks me up, but the most frequent questions are about protein for some reason.