Here's a bit of a blackhat linking tip, that I feel is really whitehat.

If your host has decent logs, it will track all "referers", which are pages that link to you site and have sent you at least one person.

What you need to do is make a list of all your referers, then run a check to see which are indexed in the search engines, and which are not.

Now, take the list of the URLs that are referers that are NOT in the engines, and get them in the engines. You can do this by pinging each URL, or by making a page with links to all of them, then linking to the page with your more powerful pages.

If you have a mature site, you may have a lot of links that aren't giving you any juice because they aren't in the engines. Do what you can to get them in the engines.