It really depends on the circumstances. If the link or post is likely to stir up a board war, no. If it’s an interesting post, and relevant to a discussion that’s already going on, then a link is usually OK. Treat it like something you saw on CNN.com, for example.
Also, I forgot to mention that issues on or about other boards should stay on those other boards. If I set up the Bodoni Boards and someone comes along and makes offensive posts, I am not allowed to come in here and Pit him or her, even if s/he isn’t a member of this board, as it might become a board war. If I used my admin powers to make life on the SDMB miserable for that member, I would be kicked off the staff. I also think it very likely that I would be banned immediately, no warning. Ed would probably come over to my house and sow my lawn with salt and things like that.* If two SDMB members are also members of the Bodoni Boards, and they have an argument on the BB, they are NOT allowed to come over here and pit each other. If someone has a problem with the BB, they shouldn’t come to the SDMB to bitch about it. This goes for boards that are not associated with the SDMB, too. If you have an issue with Fark or Something Awful, get it resolved on those boards.
*Just kidding. He wouldn’t do that. He has more respect for the landscape than that.