I hadn't known how intellectual-property law worked with regard to recipes for making food, but during a conversation with Mary Anne the other day it occurred to me that computer algorithms are often described metaphorically as recipes, and that in the US, you can't copyright an algorithm but you can patent it. (Whether that's a good or reasonable idea, and whether the algorithms that the US Patent and Trademark Office gives patents to are actually deserving of patents, is a subject for another time.)
Mary Anne pointed out that it would be awfully hard for a recipe to meet the patentability requirements, particularly novelty and non-obviousness. I was still curious, though, so I dug around a little and confirmed that The Web Knows All; specifically, an IP site has a page that clearly explains the issues involved for both copyright and patents for recipes.
The short version (which is also pretty much what the US government's recipe copyright page says) is that a list of ingredients cannot be copyrighted (so you can exactly copy a list of ingredients, making no changes at all, and still not violate copyright), but that an accompanying explanation or set of directions can be copyrighted if there's "substantial literary expression" involved (which means more than just simple straightforward directions). Also, the order of a set of recipes in a cookbook is copyrighted, if the creator of the cookbook arranged them in a particular order rather than (say) alphabetically.
As for patents, what Mary Anne said is right: you could theoretically patent a recipe, but you might have a hard time convincing the PTO that it was new and non-obvious. On the other hand, it's apparently trivial to convince the PTO that any given software algorithm is new and non-obvious, so maybe if you disguised your recipe as software it would be easier. . . . (Not that I have any opinions on this subject, nope, not me.)