I recommend Blue Ice Royal. With the caveat that it is not really 'fish oil'; it is a blend of high vitamin butter oil and fermented cod liver oil.
For those who keep their Omega-6 intake low, and therefore don't need a hefty dose of Omega-3 to strike a good balance, this product may be a good choice to fulfill all your fat soluble vitamin and Omega-3 needs.
Personally, I use the Canadian "Health Balance" brand made by Costco, which is molecularly distilled. I also use a liquid fish oil, "Omega First", which is on the IFOS listing under "Health First"
I wrote an article a while back on fish oil, which goes into selecting brands a bit: http://confessionsofacrossfitcoach.blogspot.com/2009/11/everything-you-wanted-to-know-about.html
I take the Costco brand.
Here are some fish oil brands normalized for costs:
I just took the leap and ordered Carlson Laboratories Cod Liver Oil.
Here's a really late answer to this one but I'm going through old entries and think this is a solid recommendation: Spectrum Essentials Fish Oil capsules, from wild-caught small fish (anchovies, mackerel and sardines). The label says it's third-party purity tested to ensure PCBs, dioxins, mercury, lead and other contaminants are below detectable limits.
Per two capsules you get:
EPA: 360mg DHA: 240mg Other omega 3: 200mg Omega 6: 50mg Other PUFA: 80mg Monounsaturated: 450mg Omega 9: 185mg
Other ingredients: non-GMO vitamin E and gelatin.
My local WF has them on sale for 50% off right now. At 14 bucks, it's a deal.
When I'm taking fish oil I take this one It's pretty strong: 1.34 g omega 3, 400mg DHA, 600mg EPA per teaspoon. It's not fishy tasting, but has a light lemony-orange flavour. Also the vitamin E in it is a natural source rather than the awful increases-mortality-by-displacing-actual-vitamin-e-store kind!
They also do caps, but I find a spoon of this far more convenient than umpteen many pills to get the same amount.
I've tried GNC Triple Strength pills before, but I'm hooked on Carlson Lab's The Very Finest Fish Oil (Lemon Flavor) these days - way easier than getting your daily dose in pill form. It's super cheap if you buy it online from The Vitamin Shoppe.
I use Sonne's or Twinlab CLO. Cheap, work well and contain no soy.
Cheaper is not always better. I second the Blue Ice Royal. Only fermented CLO on the market. I also take http://www.newchapter.com/product-categories/whole-fish-oil when out of BIR.
Robb Wolf has spoken in his podcasts a great deal about fish oil, quality, and marginal benefits. His stance is that there is only a marginal increase in benefit as quality goes up. This quality would refer to highly refined fish oil with any potential impurities removed. He has essentially recommended to just buy the CostCo generic brand "Kirklands" as it is cheap and he was suitably impressed with their explanations of the manufacturing process and standards.