The Washington Post has an interesting article titled Can a Recipe Be Stolen? . It addresses the question of copyright and recipes. Can recipes be copyrighted? If you take an existed recipe, and change around a couple of ingredients, does it make it your own? How much change is enough?
My own guidelines for posting recipes here is: if there was an original recipe that is widely available, either in printed form or on the web, I make sure to cite it even if I change some things around. If I try a recipe that's online without changing anything about it, I simply post a link to it here in in the main blog articles, or in my del.icio.us  under the tag "recipes". If it's a recipe that I either came up with sort of on my own, or is a classic (such as many of my Japanese recipes for things like sushi rice) then I don't cite it. Many classic recipes I've more or less inherited, from various people like my mother, but I can't remember what came from where in most cases.
As for my own recipes posted here, they are published under the nicely comfortable Creative Commons  license that appears as a footer on every page.
How do you handle recipes you post online? Do you worry about copyright at all? Also, what rights if any do you retain for recipes you do write about?