The main way is called Google bombing. To do it, you just wrap the link around the text you want associated. It’s behavior conditioning for search engines. The archetypal example is putting the text “miserable failure” in a link to http://whitehouse.gov/president/gwbbio.html. Try it here: google.com/search?q=miserable+failure.
That works because many persons put the HTML into their web pages. Google associates the link with the text and the frequency of its appearance lends it authority. Hence, “miserable failure” gets the biography of George W Bush as its #1 result on Google. Interestingly, on MSN it gets Dick Gephardt instead. I suppose that about sums up the politics of Google v. Microsoft.
I’ve been waiting for an excuse to do some search bombing myself so here we go.