Sardines.Mackarel.Herring. 
Are you gagging yet? If you are, it's a shame.They're fairly cheap, high in alll sorts of good stuff, more plentiful, and less polluted than salmon and tuna. After trying out a variety of brands I've found lots of varieties I  love. Since I can't take them to work and stink up my cubicle, they're usually what I eat when I get home starving, and theres no leftover protein in the house. Most of the time, I pop oven a can, throw  some  mayo on it,  and a little sugar free pickle  relish and eat it out of the bowl,  but  here's what I  do if  I can wait to actually  cook it first:

Mackarel:  mush up  with an  egg, make patties, fry in a little coconut oil. Serve with avacado. Even my parents thought this was disgusting over the phone, but I really like it. Macakarel isn't that much more fishy than tuna so I don't get the gagging.

Sardines with the heads on: I  bake at  400 in the air grill  until they get  crispy. My version of a fish stick!

Ok, Now where to get it:
1.) The local Russian grocery store: man, I love this place! If you're In Salem, Oregon, Privet Foods is awesome. Best  swiss cheese ever, but back to the fish- they have  dozen of  varieties of  canned fish some in sauce, some in oil. I have never found a variety here I didn't like, even salmon in tomato basil sauce.It sounds weird, but  tastes terrific. This place is  more expensive but it's a great  treat  that I can stock up on  when i'm flush then rely on when I'm broke. They also carry a brand called Ahmad Tea  that I  reccommend.

2.) health food /  gorumet stores.  The one I go to occasionaly carries locally caught (Oregon coast) Alder-smoked canned tuna. Om nom nom. Problem is, it's like $7 a can. Worth it? Definitely, but ouch! Something I'd treat myself to for a  road trip or special picnic.

3.) Big Lots/Canned Food Warehouse: a bit of a risk, so don't buy a large amount until you've tried the variety/brand first. Founds some great stuff here, and some that was just "meh".Canned foods at least in my area has a guarantee, so of it's really bad, you can get your money back.

3.)  Costco: A lot of people like their albacore tuna, but I think it's bland. They sell Chicken of the Sea chunk light for a pretty decent price, so it's one of my staples.

4.) Trader Joe's. Doesn't everyone know this place ROCKS? No Bht in the cans,  reasonable  prices and  all sorts of canned fish. While you're there, the frozen asparagus is the BEST!, and they sell some of the best Greek yogurt on the market. 

Now the one brand I would advise against:  Bumble Bee.  Every product I've tried of theirs has been bad. The sardines were disgusting ( even the neighborhood alley cat refused them) and their so called "chuck white albecore" is a pathetic amount of flakes that looks like cat food. Don't waste your money

A great place for reviews  for sardines:  http://www.sardinesociety.com/