I do not like a lot of the foods that contain omega-3s so I seek out alternatives to get my supply of them. One of my favorites is Flax Seeds. I add them to my morning oatmeal, use to substitute for some of the fats called for in baked goods, etc. If you aren't including flax seeds in your diet, give them a try.
Packed with omega-3s, flax seeds have a mildly nutty flavor that is well suited to blending into other foods. Flax seeds are hard to digest whole so you should grind them or buy them already ground.
Note: I store mine in the refrigerator.