Free SEO tools
Paid tools are essential when you need advanced features,
increased limits, historical features, or online support.
Sometimes, in order the wanted aim a free tool does the trick.
A/B Testing; Visual Website Optimizer allows you to run A/B tests.
Keyword Eye
Keyword research done by adding rich visualizations — essential
when you want to move beyond keywords to valuable concepts.
Ahrefs
One of the more popular link research tools, Ahrefs offers a
large index and nice anchor text distribution charts. Mostly a paid tool, but
they offer some free data.
Yoast WordPress SEO
Plugin
If you could only choose one WordPress plugin for you site, the
first would be from Yoast, and so would the second.
Virante SEO Tools
Virant offers a number of high quality SEO tools to the public.
Social Mention
Social mention offers real-time social media search and
analysis. Enter a search term and see who's sharing what, right now.
SEOQuake
More raw data than any other SEO toolbar out there
EO Toolbar
On of the most popular tools available, The SEO Toolbar puts a
ton of information at your fingertips including backlinks and competitive
research.
SEO Tools for
Excel
You don't need to be an Excel ninja to use Niels Bosma's SEO
Tools for Excel. This plugin does so many things many SEOs won't work without
it.
The most
popular of all the analytics tools available, Google Analytics continually
innovates and sets the standard.
The Google
Analytics API is great for building custom reports and tools, and also for
pulling data straight into Excel or Google Docs.