● Keywords Everywhere Great keyword tool Chrome and Firefox extension. (now paid)

● Answer The Public Aggregated view of the questions asked to Google & Bing.

● Keyword Keg Another free keyword tool, you can import lists and export 20 results.

● Wordtracker Scout Displays what articles are about on keyword cloud.

● LSI Graph Generate a list of semantically related keywords and best performing content.

● Google Trends Compare one keyword to another over time

● Keyword Finder Uses Google's autocomplete API to find many keywords.

● KeywordTool.io An alternative to Google keyword planner.

● Merge Words Takes words from 3 lists and merges them together into one.

● Cognitive SEO Keywords Analyze keywords and get suggestions.

● Seed Keywords Grow your own seo keywords from suggestions from your friends.

● Keyword Density Checker Remember to write for people, not SEO, don’t over optimize.