Termexplorer is a nice keyword analysis tool that hooks straight into Google’s Adwords API. You can get a free account with 3 queries you can run a day, so you can try it out. The tool is pretty impressive listing all data from Google’s Adwords Keyword Tool.
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Rankshaper is a real-time, on page SEO ranking tool and keyword discovery tool. It helps you identify new ranking opportunities and gain access to new niche markets. Add the search terms your visitors are using to find you and discover new terms and new combinations, while tracking performance.