Keyword Snatcher is the powerful and simple to use keyword research tool
Reddit Keyword Research Tool that can extract keywords from Reddit
Keyword Research and Web Page Strategy-Good Keywords
Domain Research Spot| Keyword Reseach SEO PPC opportunities and outsmart your competitors
Think with Google-Google Trends to Your Marketing Tools
Content Idea | Market Research Tool | FAQ market research
QuestionDB is a tool that lets you search a massive collection of user questions to get original ideas for new content.