It's best just to post the URL to the site's mainpage, otherwise it may link to an article you wrote, include your registration/member ID number, etc, giving away your alternate username.

Looking at the other aspect of it, providing a link to your profile, posts, etc usually won't let them see your private registration information (anything that's not in your public profile) because most sites rely on cookies. However, if the site relies on session IDs in the URL, such as www.website.domain/username/edit_profile/sessionID=0123456789, then it may be possible that giving them the link would grant them access to view and even edit your personal/private information. Again, all the more reason to keep the URL simple.

Finally the spam rule depends on the context. Some general things I suggest include:
* Don't include links to personal/favorite sites in your signature.
* Don't link to a site if it's unrelated to the topic being discussed.
* Don't post a question or guide elsewhere and then link to it. Instead, post the content without the link.
* Watch how frequently you link to a specific site.

You may also want to review this article concerning proper netiquette, which covers more than just linking. Personally, I wouldn't see a problem with the links in this case since it goes directly to being able to provide a detailed answer.

Hope this helps,
John