The Google search engine now drives the primary search
  results on Yahoo. While this is certainly an improvement
  for users of Yahoo search, it's a disaster for many
  businesses that counted on their Yahoo listing to deliver
  substantial traffic.

  This change has also led many site owners to question the
  value of a listing in the Yahoo directory. In this article,
  I will outline the pros and cons of maintaining, or paying
  for, a Yahoo listing. In the process, I will delve into
  more details of the recent changes.
 

  Argument #1: Yahoo Listings Mean Link Popularity

  Pro:
  Even if the Yahoo listing itself delivers little or no
  traffic, other search engines will rank your website higher
  if it's listed in Yahoo. Because Yahoo is so important, a
  link from Yahoo counts more than a regular link. Thanks to
  its higher "PageRank," Yahoo means even more to Google.

  Con:
  Yahoo listings do not deliver nearly as significant a
  contribution in this area as you might think. You can
  verify this by doing a "backward links" search on Google
  for any Yahoo-listed website. The most important links are
  listed first, and the Yahoo listing is rarely even on the
  first page of links for top ranked sites on Google.
 

  Argument #2: Listed Sites Look Better In The Search Results

  Pro:
  Websites with a Yahoo listing show up in the combined
  Yahoo/Google results with their title, description, and
  category from the Yahoo directory. This may boost the
  response when the site appears in the search results. This
  applies when the URL listed in the results is the same as
  the URL in the Yahoo listing. 

  Con:
  Results listed with Yahoo information include a link to
  the site's category, which may prompt surfers to pass over
  your listing and go to the category. Sites without Yahoo
  listings have the more inviting "search within this site"
  link, which leads to more results exclusively from your
  site.
  -------------------------------------------------------

  So, Is A Yahoo Listing Worth It?

  If you have a non-commercial site and can get listed for
  free, of course! If you're not one of the lucky few,
  though, you have to evaluate whether it's worth $299 a year
  for what amounts to a better than average incoming link.
  Everyone must make their own decision. If $299 is small
  compared to your total marketing budget, it may be easier
  to just continue paying. My own listing expires in March,
  and I don't intend to renew it.
 

  How Can You Profit From The Changes At Yahoo?

  The obvious answer is that you must take steps to improve
  your own position in Google's search results. Google's
  rankings are made up of many factors, but the dominant
  factor is "PageRank," which is based on the number and
  quality of incoming links from other websites.

  Therefore, the first step in improving your position on
  the Google search engine (and now Yahoo) is to improve your
  site's link popularity. This takes time, and trying to take
  shortcuts can get you into real trouble - Google doesn't
  like "link farms," or any program designed to artificially
  boost your link popularity.
 

  Finding Quality Link Partners Through Google

  Since only links from quality sites will count for much
  with Google, let's take a quick look at how you can find
  these sites. Start by targeting the sites that link to
  existing top-ranked sites. You can do a backward links
  search for any site by typing "link:http://www.domain.com"
  in the Google search engine.

  An even faster method is to use the Google toolbar
  (http://toolbar.google.com/), which requires Internet
  Explorer 5 or greater, running on Windows. With the
  toolbar's advanced features enabled, you can conduct a
  "backward links" search from the "Page Info" menu for any
  site you visit.

  Since Google lists these results in descending order by
  "PageRank," you can quickly determine the best places to
  get links by doing backward links searches on the top 10-20
  sites for your desired search terms, and seeking links from
  the top 10-20 places that link to them.
 

  Links Are Not Enough: Optimizing For Google

  While "PageRank" is the dominant factor in Google's
  algorithm, it's not the only factor, and you still need to
  optimize your web pages. This can be a complicated topic,
  but the most important factors are:
  - Keywords in the title of the page
  - Keywords in headings on the page (H1 or H2 tags),
    especially the first heading.
  - Keywords in the body text of the page, particularly the
    first paragraph.
 

  Don't Complain, Act!

  By some estimates, Google now controls 2/3rds of the
  searches conducted on the Internet in a given day. Not only
  is Google.com extremely popular in its own right, but
  Google also controls the search results on popular portals
  like AOL and Iwon.com - not to mention Yahoo.

  A lot of website owners are complaining bitterly about
  this change. All the more reason for you to take action
  now, while so many of your competitors are busy licking
  their wounds. With a little planning and effort, you could
  be in a dominant position on Google before they even get
  started.

  I wish you success...

  About the author:

  Dan Thies is the author of "Search Engine Optimization Fast 
  Start," the ultimate beginner's guide to higher search engine 
  rankings - available today at http://www.cannedbooks.com