Major Pay Per Click Search Engines

Yahoo! Search Marketing
Put your business in front of potential customers at the precise moment they're searching for what you sell.
LookSmart
LookSmart is primarily a human-compiled directory of web sites. It gathers its listings in two ways. Commercial sites pay to be listed in its commercial categories, making the service very much like an electronic "Yellow Pages." However, volunteer editors at the LookSmart-owned Zeal directory also catalog sites into non-commercial categories for free. Though Zeal is a separate web site, its listings are integrated into LookSmart's results.
FindWhat.com
Findwhat.com is part of the MIVA network. Advertise here and all over the MIVA Network and you'll be in the right place to reach your customers at exactly the right time - when they are actively looking for your products and services.
google AdWords
The google AdWords program places paid listings within google's search results, as well as on some other sites that carry its listings.
Microsoft adCenter | Search Advertising
Microsoft adCenter is pay-per-click advertising for budgets of all sizes.
MIVA (formerly Findwhat.com)
MIVA provides a wide range of tools to help businesses grow, including performance based marketing products to help businesses find new customers, monetisation tools to help online publishers generate advertising revenue from their websites, and ecommerce enabling solutions that let internet retailers conduct business online.