Disclaimer: I'm not a moderator or affiliated with ChefTalk in any way other than the fact that I love the wealth of experience and information available here.
Having said that, I've never heard of providing a link to a site being a problem. I tend to think of it as free advertising for the site you link to. Using information, graphics, etc. from a site without permission can lead to problems with some sites but as far as I know there is no legal recourse to simply providing a URL link even if a site didn't want you to do it. I'm pretty sure it falls under the realm of "public information". You make your URL available to the public (when you put it online and especially after registering with a search engine) and it becomes public information which doesn't share the legal protection that private information gets. The polite thing to do is exactly what you're doing: ask permission. As far as legality goes though, it doesn't really matter if you ask or not as long as you use a text link or a graphic that you created yourself.