Google AdWords tool shows keyword suggestions based on keywords you add, or based on a website’s content. You also get info on keyword competition and search volume. Use this info for SEO, or PPC advertising on AdWords. Related posts: Google Keyword Search Tool Stats On PPC Ads Keyword Density Checker

Search by URL or by keyword: Spyfu shows cost per click for a keyword, click per day, cost per day, search volume, number of search results and advertisers (limited) and their ad copy. All info is based on Google AdWords. Related posts: Get New Keyword Ideas Google Keyword Search Tool