I may not be the best one to ask, as I am still formulating the vegetarian diet that is right for me...
the other options that I am aware of are:
mycoprotien, derived from mushrooms
seitan, or "wheat-meat"
beans, including soy, of course
tree nuts and such
for me, the idea that we have to replace that slab of cow or pig with some equally dense form of protein is sort of out-moded. It seems when we focus too much on one thing (i.e. protein, low-carb, saturated fat, etc.) we miss the basic idea that what we should eat is a variety of whole foods, organically grown, as fresh as possible and with little to no industrial processing. Protein is found in many of those things.
I just finished a great book called In Defense of Food, it really rearranged some of my thought patterns...