Overview: These are free which will help you find which keywords to target & how competitive they are. Here is a video offering an introduction to keyword research At the bottom of this page are a link to a free keyword research PDF & a few more free background videos about understanding keyword research & using keyword research tools.Keyword Suggestion Tools   
·  Wordtracker Free Keywords - free keyword suggestions from Wordtracker. Wordtracker also has a more advanced paid version, and sells top keyword reports. 
  ·  Google AdWords Keyword Suggestion Tool - recommends keywords based on a keyword you enter or a URL you have the tool analyze 
  ·  Google Suggest Tool - shows frequently search for phrases starting with the words and letters in your query. 
  ·  WordStream Keyword Tool - allows you to export a list of thousands of keywords for free. 
  ·  Keyword Discovery - free keyword tool from Trellian. Trellian also has a more advanced paid version of Keyword Discovery. 
  ·  Microsoft Keyword Forecast - shows predicted Microsoft search impression count and historical trends. 
  ·  Wordze - nice for generating decently large keyword lists quickly and inserting them into paid search campaigns. 
  ·  Yahoo! Search Marketing - Yahoo! has a keyword research tool inside their platform. It is really bad marketing of them to only have the new tool accessible inside their platform, while neglecting their old keyword tool.