I am new to this site and have seen some great information, however I need to add a couple factual pieces of info regarding salmon, their types, sources, and quality. My experience comes from over twenty years living and working in northern Alaska, so I tend to know a bit about salmon. I have experience with every type of salmon out there, including handling, cooking, sampling, and seasoning, so I'm not some idiot providing info.
TYPES
As a previous member posted, there are basically five types of salmon; king, coho, chum, sockeye, and pink (not worth talking about, great pet food). King is the best, with texture that is second to none and flavor that just melts in your mouth. Be careful though, sometimes it is too rich for some people. Coho (aka Silver) is a great medium priced fish with quality far superior to chum but at a very similar price point. Yukon cohos are a great choice at a reasonable price point. Chum salmon are a good fish, but only if they come from a quality source and they need to be fresh. Previously frozen chum are best used for pet food. Sockeye is most well known for it's bright red color (which has no bearing whatsoever on taste). The quality is better than chum but not quite up to coho. Sockeye is most commonly used in restaurants and display cases because the bright red color draws people attention.
OIL
Salmon quality is almost entirely based on the oil content of the salmon. The higher the oil content, the higher the quality. With salmon, as quality goes up, fishiness goes down, seasoning required goes down, and taste/flavor goes WAY up.
With salmon they are born in fresh water, swim down the river out to the ocean, play around for a couple years, then swim back to where they were born. However, once they re-enter fresh water they quit eating. So based on the distance from the ocean to where they spawn determines the amount of fat (oil) required for them to make the journey. So in other words the longer the river the greater the oil content.
RIVER
Copper river, although well known for their great flavor, is actually a great marketing campaign on an average product. What makes it so great is that the competition is very poor (almost all farm raised) and the marketing has been nothing short of unbelievable. Additionally, the Copper River fishery takes outstanding care of their salmon when they are caught, ensuring that every fish is of the highest quality.
However, it is important to remember that the Copper River is only 300 miles long, compared to other rivers in Alaska like the Yukon, which stretch over 2000 miles. Copper River Salmon is great, but if you get the chance give Yukon King (the most well known), Kuskokwim King, or Yukon Fall Cohos a try.
WILD VS FARMED
There was a post in June about farm raised salmon having higher oil content. This is not true unless you are comparing it to northwest or bay/sea (Prudoe, Bering, etc) salmon. For example, the oil content of Yukon King is around 30%, the highest of any wild salmon in the country and in the top five in the world.
FREEZING
Katie posted back in June wondering how long salmon would last in the freezer. It really depends (sorry). For the best freezer life, fully prepare the salmon before freezing (deskin, debone, etc), then place the salmon in the freezer for 24 hours. Remove, dip in salt water (called glazing), then wrap in saran wrap, put in a ziplock, and refreeze. If done well this will be good for about a year.
Sorry to ring on for so long but I wanted to help everyone get the facts. So when you are shopping for salmon don't only look at the color (although important), look at the type, source, and whether it is fresh or frozen. And remember, anything Atlantic is farm raised, no matter what the tag says.
And feel free to email me if you have any questions I can help with. By the way, my favorite salmon recipe is a skinned filet rubbed down in Lebaneze Breeze (garlicgarden.com) and Spade L Ranch (available at Albertsons in the Seafood area), then cooked medium heat on both sides until the center turns opaque.