I used to get my omega-3 from flaxseed oil. Then I encountered problems with the flaxseed oil going bad, in the sense of losing potency. (It did not smell bad.) I switched to flax seeds, which I grind and eat with yogurt. This is more difficult than drinking flaxseed oil.
From Peter Spero I have learned of a possible new source of omega-3: camelina oil. Camelina oil, unlike flaxseed oil, contains high levels of anti-oxidants, which protect it from going bad. Camelina is cheap to grow and can be grown where other crops cannot.