SEMRush - All-in-one Marketing Toolkit for digital marketing professionals.
Aves API - Aves API is the insanely fast SERP API that enables you to scrape Google search results without blocking.
SEOmator - SEO website analysis & audit tool
SERPs - SERPs is a rank tracking software for large scale SEO.
Lumar - (Previously DeepCrawl) Hosted SEO spider to analyze and find problems with websites.
SEOquake - SEOquake provides a browser extension to conduct on-page SEO audit.