A few years ago, for a period of about five years, a significant part of my job was 'optimising' the company website, at which I was very successful. You could type in almost any relevant search term and my company's website would ocupy at least 5 of the top ten search results.
Not very ethical, because mainly what I did was embed loads of search terms hidden in the code, set up a number of carefully named redirect URLs and mirrors, plus the usual term postioning, font emphasis etc. Our sites would never could close to passing W3C validation because the code was so heavily manipulated. All the stuff Google tell you is disallowed basically. But the warnings are scare stories, none of it ever came back to us, we were never removed from any lists or added to any blacklists.
It was about 5 years ago I changed jobs so I'm not in the business any more and things might have changed, but we always worked on the principle that they didn't care enough about small companies and the lesser used keywords we were interested in to bother with us, and it worked just fine.
[Disclaimer: don't try this yourselves folks, they might just have nailed this kind of thing by now.]
On a more commercially acceptable note, we also found that spending money on google keywords was a very good investment.
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