A guide to redesigning a website without affecting SEO | Search Engine Watch
Nibbler - Test any website
SEMrush - service for competitors research, shows organic and Ads keywords for any site or domain
SEO Tools - Search Engine Optimization Tools
INFOGRAPHIC - How to change website domain name (And keep Google ranking)
Attracta SEO Tools & Managed SEO Services
Majestic®: Marketing Search Engine and SEO Backlink Checker
How to build a bigger website – subdomains or subdirectories? Part 1 | Digital Brand Insider
Official Google Webmaster Central Blog: Best practices when moving your site
8 Most Important SEO Data Points of Any Website | SEJ
Website Traffic Estimates by TrafficEstimate.com
PageRank, website value review, page rank stats, keyword seo analytics
Majestic SEO : Backlink Checker & Site Explorer
Website SEO Score Tool