Pay-per-click (PPC) advertising is one of the most common alternative means of improving your search engine visibility. These ads appear at the top and on the right side of search results pages, and you only pay to advertise when your link is clicked.
PPC advertising is not only affordable, but also fully under your control. You just need to choose the words and phrases you want to appear, and an auction system will determine your placement. Google Adwords, Bing / Yahoo and Facebook are all common purveyors of PPC ads.