Maybe some deli meat? They're generally pretty lean, but be careful about carbs, sometimes they use sugars and spices on them that can add up. If you ask at the deli counter in the supermarket, they should be able to tell you (I had to ask once and they whipped out a book with all the info!).
Or cured salmon (like the kind they use for lox and bagels) with some cream cheese?
I have a hard time fitting cooking into my schedule, so sometimes what I do is cook a lot of something on Sunday that I can use the rest of the week, like maybe chicken or some steak.
Oh, and how about shrimp? Costco sells bags of pre-cooked frozen shrimp. All you need to do is take a few out and let them defrost (to defrost quickly, just run them under some water). I use cocktail sauce on them, but I am very careful to measure the sauce because the carbs add up quickly. You could probably throw some on a salad too.
