OpenGraphTool.com - Open Graph Checker Tool
Majestic - Majestic - Link intelligence tools for SEO and Internet PR and Marketing. Site Explorer shows inbound link and site summary data.
OpenGraphTags - Open Graph Tag Simulator
MetaTagTool.com - Meta Tag & Open Graph Tag Generator, Simulator, & Analyzer
Moz Link Explorer - Search engine for links Perform competitive website research.
Moz - Backed by industry-leading data and the largest community of SEOs on the planet, Moz builds tools that make inbound marketing easy.