Pay Per Click (PPC) is generally the small text ads that visitors see, when they are browsing websites, search engines, social networks etc. Google Adwords is by far the most effective PPC network; but Yahoo, MSN, Miva, Facebook etc also offer similar networks, which could be effective from case to case.
PPC campaigns, if managed efficiently, can do wonder in small budgets, since it follows a bidding system. It can reach the niches and certainly deliver. Identifying key phrases, creating ad copies, optimizing the landing page and constantly monitoring and managing bid levels are essential factors in this endeavor.