Prior to any search marketing campaign, keyword research should take priority. This is the process of not only selecting keywords and phrases that are relevant to one's business but ones that people are actually searching for. While a portion of this requires good old common sense, actual data and statistics are a necessary ingredient in developing a good list of words to target.

This is where keyword research tools come into play. I have assembled a list of the most popular keyword research tools, some of which are paid services while others are free. Hat tip to Chris Logan whose post at Small Business Ideas Forum inspired this entry.

Leading Keyword Research Tools:

• Keyword Discovery
  Prices start at $49.95 per month or $479.40 annually ($39.95/mo.) This is the keyword research tool we use at SearchRank.
   
• Wordtracker
  You can order Wordtracker for as little as one day for $7.93. They also offer weekly subscription at $26.44, monthly at $52.87 or annually at $264.36.

Free Online Keyword Research Tools:

• Digital Point's Keyword Suggestion Tool
  Offers options to search Overture and Wordtracker data.
   
• Google Keyword Tool
  Generates potential keywords for your ad campaign and reports their Google statistics, including search performance and seasonal trends.
   
• Niche Bot
  Offers options to search Keyword Discovery, Overture and Wordtracker data.
   
• Overture Keyword Selector Tool
  Displays search data from Yahoo, All the Web, Alta Visa and other search partner sites.
   
• Pixel Fast
  Uses data from Overture.

Free Desktop Keyword Suggestion Software:

• Good Keywords
  Free Windows based desktop software, 500Kb download, digitally signed and safe to install.
   
• Keyword Spider
  Free desktop software that gathers tons of keywords from other people's websites using sneaky spider technology (that is what their site says... not me).
   
• Keyword Tumble
  A free keyword research marketing tool that takes your existing keyword phrase and generates multiple variations of it, simply by mixing the words in each keyword phrase around.

Other Free Keyword Tools:

• 7search
  Data from 7Search.com queries.
   
• Iota Web
  With the ability to search a growing database of tens of thousands of high-dollar AdSense keywords, Iotaweb allows publishers to find the keywords and key phrases that will allow them to focus their content to monetize their site most effectively.
   
• Keyword Difficulty by SEOmoz.org
  Analyzes the competitive landscape of a particular search term or phrase. This tool issues a percentage score and provides a detailed analysis of the top ranking sites at Google and Yahoo.
   
• SEO Book Keyword Suggestion Tool
  This tool shows top keyword phrases from Overture. Also links to other keyword research tools, including: Overture View Bid, Google Suggest (popular Google search phrases), search results from each of the major engines, Google AdWords Keyword Sandbox Tool and NicheBot. Also links at various vertical databases, blog searches and tagging systems to show you the top results from other information sources.

And finally if you wish to hire a professional to conduct your keyword research for you, I highly recommend Dan Theis of SEO Research Labs. This is Dan's niche and he has years of experience behind him.