Hi! Here on Cookie Connection, we encourage members to share URLs with any clips (i.e., photos or videos) they post, as long as those URLs are relevant to the clip. For instance, linking back to the tutorial for the cookie is completely fair game.
NOTE: We encourage you to share your tutorials directly in our blog too, though there we ask that you post substantial information content, text and at least one photo, and not just the URL. From time to time, we'll be featuring especially informative blog posts, so that is a great way to bring your work more exposure.
HOWEVER, PLEASE BE CAREFUL WHEN POSTING A URL WITH A CLIP:
1. Right now, the site will not easily accept a URL in the clip title or caption areas. (The site does not know how to parse URLs in those areas, so areas of the site, particularly the home page, can experience formatting issues if URLs are entered there. The site will also not automatically live-link to URLs entered in those fields.)
2. Hoop.la, the site host, is investigating a possible change to allow for entering URLs in those areas. They are not sure it is possible, but I will keep you updated here. In the meantime, PLEASE INSERT ANY URLs INTO THE COMMENTS AREA UNDER YOUR PHOTO/CLIP, IMMEDIATELY AFTER YOU POST THE CLIP. URLs will be happily accepted and linked to there! 
Many thanks!