I just found the National Resources Defense Council’s Mercury in Fish wallet card printout that helps you remember which type of fish typically have what types of mercury levels. In the back of my mind, I always have known that I need to eat more fish, though I can never remember which ones tend to have higher levels of mercury.
The printout also gives you recommended guidelines on how many servings you should eat (moderation is key, even with fish that can contain higher traces of mercury). It also provides some good guidelines if you want to continue eating canned tuna.