What are some sources of protein ?

Greek Yogurt, plain. Add some seasonal fruit.
Tofu
Pulses ( lentils, chickpeas, beans ( all kinds))
Cottage Cheese
Sausage

Aside meat, as you mentioned, I gotta add a third vote for greek yogurt - I get full-fat plain Fage and mix homemade jam into it and it's amaaazing. Some people like to mix protein powder in their yogurt, but that is too thick for me.

Tuna + cottage cheese + salsa is one of my favorite protein bombs. Cottage cheese also pairs well with jam or fruit, if you prefer it sweet.

Jerky - the Krave jerky is some of my favorite, especially sweet chili beef.

Protein powder, as you mentioned. I like protein powder and whole milk in iced coffee. I also often have clif builder bars, or if I have fewer calories to spare and want something more like a candy bar, I'll have a luna bar.

ETA: One of my favorite things to do with protein powder is make protein pancakes, waffles, or protein muffins because I like having carb-y snacks and baking with protein powder is a good way to achieve a better balance. Plus, baking = win.

all dairy is protein...not just yogurt... peanut butter is not an excellent source of protein... quinoa... and all manner of beans and lentles... (including peas)... the UN has declared 2016 the year of the "pulses" all manner of beans, peas, etc.... which are better sources of protein than any meat or fish... ( I looked it up)

Vegetables!