Trade Skills PageFollow

Here's a general rule of thumb: The recipe page for a profession will link to a Recipe if the pattern cannot be learned from a trainer. And the rule of thumb for recipes is that White text = Vendor sold recipe and Green text = dropped by a mob. You can click the link to the Recipe page to see what drops it. Most recipes pre-expansion (i.e. the ones you still get on Azeroth, not in the Outlands) will not be BoP and as such can be traded/sold.

There are a lot more BoP recipes in the Outlands which prevent non-profession players from stealing a recipe from someone who can validly use it. And it also prevents people who don't have that profession from even being able to roll on it, should they be in a group with others.