The only type of linking (besides porn and spam, of course) that will not be allowed on our site is when members solicit people to leave our site for a competing service. That's just common sense. We won't allow people to use our site to promote a competing service any more than a brick-and-mortar store would allow his competitor to paste flyer's all over his walls. However, people are always welcome to link to any online resource, whether it's on our site or any other site, in order to share useful information with fellow members.