Google SERP Snippet Optimization - SEOmofo tool replicates the appearance of a snippet in Google SERPs, which allows SEOs to optimize a page title and description for maximum click-through rate.
LinkChecker - LinkChecker is a free, GPL licensed website validator.
Ahrefs Backlink Checker - With the world's biggest index of live backlinks (over 15 trillion), Ahrefs Backlink Checker will show you the most complete backlink profile for any website.
Dead Link Checker - Check for broken links on any website
SiteChecker Google Cache Checker - Check the last date when website was cached by Google
Pulno - SEO Audit and Website Analysis. Pull up your SEO.