For websites that are interested in improving their SEO or advertising on paid search, there is one absolutely crucial thing that they're going to need to make their efforts a success.
If you haven't guessed what that one thing is, yet (or read the title of this post), I'll go ahead and tell you. It's a keyword list, of course!
Since there are thousands of ways that people can begin searching for content or a type of product or service online, creating your own extensive and useful list can be quite the chore. No worries, though, because there are plenty of great keyword research tools on the Web that you can use RIGHT NOW that won't cost a cent.
That's right - all of the online keyword research tools in the big list that follows are totally free. So what are you waiting for?
Google Ads Keyword Tool
Easily the most popular entry on this big list, Google's AdWords Keyword Tool lets users enter a keyword from their niches and look for those exact terms or for phrases containing them through advanced options and filters.
Moz Link Explorer
This service from SEOmoz is ideal for researching your competitor's keywords.
SEMRush
Use SEMRush to get data on the top 10 keywords that your competitors are getting traffic from on both paid and organic search.
Moz Free SEO Tools
Another SEOmoz tool, Term Extractor lets users enter a competitor's URL to receive one, two and three-word search phrases that the site is targeting.
Alexa
Alexa lets users see search engine queries from their competitors and the percentage of traffic that those terms bring to their sites.
Wordtracker Keyword Questions Tool
The majority of the full set of tools provided by Wordtracker are totally free to use, and they allow users to fine tune and get specific data about the relevance and popularity of certain topics within their niches.
SEO Book Keyword List Generator
This keyword research tool is actually powered by Wordtracker and generates a list of related terms for a user's search and provides links to keyword suggestion tools from major search engines.
WooRank
The Website Review tool from WooRank offers - no surprise - a free review of a user's website that shows the top keywords that the site ranks for on Google search, in addition to a list of its competitor sites.
KeywordSpy
This tool is also meant to help users track their keyword competitors by showing them the keywords their competitors use in their advertising campaigns, which includes AdWords, the Bing Adcenter and Yahoo Search Marketing.
SpyFu
SpyFu will analyze a site's competitor's paid search campaigns on AdWords to generate a list of organic and paid search keywords they are using.
Keyword Discovery
Keyword Discovery from Trellian lets users analyze a list of over 100 search terms related to their chosen keywords.
WordPot Free Keyword Tool
This tool will also provide users with a list of the most popular keywords in their niches, and features "Exact Daily" and "Total Daily" lists so that users can easily separate their data.
WordStream Keyword Tool
Users can get free keyword suggestions for the target search terms that they enter into the WordStream Keyword Tool.
Soovle
Speed is the name of the game with Soovle, which will return quick keyword suggestions from Google, Bing, Yahoo, Amazon, Wikipedia, YouTube and the always-popular Answers.com, along with statistical data graphs to compile all of that information.
UberSuggest
Similar to the Google Suggest tool, UberSuggest takes your base keyword term and adds a digit or letter next to it that suggests (see?) probably search term combinations.
SEOquake
This is actually an add-on for the Mozilla Firefox browser that helps user find keyword data based on keyword density.
KGen
Short for "Keyword Generator", KGen (pretty clever, eh?) is another Firefox add-on that scans the Web page a user is on to determine its keywords, making it perfect for competitor and keyword density research.
Ranks.nl
This online tool offers users a plethora of different variations and combinations of their keywords and phrases.
TweetVolume
Built for social media campaigns, TweetVolume lets users see how many times a specific keyword or phrase has been mentioned on Twitter.
Keyword Typo Generator
Not everyone spells every word right every time they try. That's why the Keyword Typo Generator from SEO Book comes in handy, as it generates a list of the most common misspelling for a particular keyword, just so you know.
Microsoft Advertising Intelligence
This PPC research tool and Microsoft Excel add-on requires a Bing Ads account and helps users discover new keyword ideas by entering the URL of their website or a list of keywords.
Google Trends
Another Google tool for the list. Trends lets users compare multiple search terms by separating them with commas. Who knew such a simple punctuation mark could be so powerful?
NicheBot Classic
With NicheBot Classic, users simply have to type in a keyword or phrase to receive the top 50 most popular keyword listings for that particular term.