We use the Nordic Naturals "Children's DHA". They're little "bubbles" (round capsules) that are strawberry flavored. My 3yo son loves them. I let him try them first and he liked them so much that I thought- wow, they must really taste like strawberry. I tasted one and Yuck!! just tastes like fish oil to me! I think it's crazy that he likes them, but he does- eats 4 a day per the recommended dosage. Usually he doesn't like medicines and such, so I don't get why he likes them, but I'm sooooo glad he does. We very rarely eat fish and he doesn't eat eggs much either (I get the eggs with 225 (mgs?) of Omega 3's). I don't eat fish often because of a food poisoning I had years ago, so I don't cook it. I know, it's terrible, but at least he eats his "bubbles".
Oh, I forgot, I also give him a serving of "Toddler Health" everyday- that has Omega's in it, too. Unfortunately the recommend age for it ends at 5, I believe (it's 13 mos-5yo). For those of you who want to check out the Toddler Health, you can go to toddlerhealth.net. (It's cheaper to buy the case on amazon, from my experience, though.)