Here is a list of the best Google Chrome Search Engine Optimization (SEO) extensions (plugins).

Search Engine Optimization (SEO) Extensions⌗

Chrome SEO⌗

The Google Chrome SEO Extension. Make your SEO tasks easier with Chrome SEO Tools, includes ‘all’ the stats and data you need.
Install Extension

SEO Status Pagerank/Alexa Toolbar⌗

SEO Status is lightweight. It will check the Google Pagerank (PR) & Alexa rank for every page. Using this will increase your Alexa.
Install Extension | Developer website

PageRank⌗

Fastest and Very light weight. It shows Google page rank on toolbar.
Install Extension | Developer website

PageRank Status⌗

Shows Google PageRank and Alexa Rank of the current web page, quick access to Whois, Alexa, backlinks and indexed pages.
Install Extension | Developer website

SEO Site Tools⌗

Pulls tons of On-Page and Off-Page metrics, Social Media info and enhances SERPs with metrics as well as GA, WMT and much more.
Install Extension | Developer website

META SEO inspector⌗

Useful to inspect the meta data found inside web pages, usually not visible while browsing.
Install Extension | Developer website

SEO SERP⌗

A simple tool to quickly check the position of a list of sites given a keyword.
Install Extension | Developer website

SEO⌗

This Chrome SEO plugin implements the SEO Playground Tool (Bookmarklet) by David Naylor. Making it easier to use in Chrome.
Install Extension | Developer website

iPageRank | SEO Tool for Chrome⌗

This plugin gets PageRank & calculates how much PR is transfered to external links, analyzes keywords, Alexa, TIC. More inside.
Install Extension | Developer website

SeoQuake⌗

SeoQuake is a SEO extension (toolbar) for Google Chrome, it shows PageRank, Alexa and tons of SEO parameters, also works in SERP.
Install Extension | Developer website

SitezMeter⌗

SitezMeter displays traffic charts from Google Trends, Alexa and Compete side by side, as well as ranks.
Install Extension | Developer website

Chrome Flags⌗

Porting of FlagFox to Chrome. Displays a country flag indicating the location of the websites you’re visiting.
Install Extension

I update the list whenever I find a good Google Chrome Search Engine Optimization SEO extensions. If you know of other good SEO extensions for Google Chrome, please let me know, so I add them to the list.