Here is a question. If you cross-link posts within your own blog or site, can it be considered as spam?
no its not and is a common practice. if you have a post that relates to another, then you can link to the other post for more info or as a reference. sometimes there can be a series of posts on a specific topic and newer posts will have link to the older posts for reference. however, too much interlinking is no good
There was a thread over on seoers forum a while ago where they were discussing Google saying that nofollow makes link juice evaporate.
Not at all. It's good SEO There is related posts plugins for wordpress or you can just link to related posts in the content.
Think of the main menu of a website or categories links in the sidebar that are sitewide links. Linking from one page to another on the same website can't be considered spam.