Internal Link Building is a new plugin that allows people to define a keyword as always linking to a given URL. This allows you to link within your site like Wikipedia, and rank accordingly.
You can also tell it to only link the first time a keyword appears in a post/page.
Another function is post-level override, so you can make a keyword link somewhere else in a given post. This lets you give good anchor text in links to friends.
A third point is that this tool lets you also define a number of URLs to link to at random when a given keyword appears. Input your list and one will be selected at random whenever the keyword appears. This makes linking to a network of sites you own in a given vertical more easy.
Finally, this will not override existing links on your blog.