There's a lot of debate about whether fish is good for you or toxic, whether eating fish is sustainable or not ecologically, whether you should look for farmed or wild-caught, which fish to avoid. So wow do I love this website: http://www.oceansalive.org
It lists most commercially available fish and seafood options and rates them on a best/okay/worst scale for your health and the health of the environment and fish populations. It breaks down how many servings a month of what type of fish are suitable for women/men/older kids/younger kids. There's a list to help you substitute eco-sustainable fish when your recipe calls for one that's not sustainable. There's even a recipe section, though I haven't tried any of them yet.