To ensure that my in-page and in-post links to other pages/posts on my blog are always correct, I use the runPHP plugin to add a call to bloginfo('url') to prefix my links, so they're always absolute. It would be nice if there were a way to access a post's or page's permalink in a post or page without having to resort to PHP.
This might look something like a wiki link:
[Internal_page_slug text to be linked]