We are continuously adding new sources*. The total count has most likely changed as soon as I wrote this sentence.
Our primary source of company related information are News, Company Websites, Social Handles of Companies, Regulator Websites. On our customer requests, we add custom sources such as Job Portals, Review Websites, Discussion Forums, etc.
We extract strategic updates (link) about companies after removing irrelevant general information noise. It means, we extract only company related unique information from all the information published on these sources. That's what makes Contify is an intelligence platform -- not just an un-intelligent RSS reader, or a keyword based alerting system, or a web crawling service.
* We can track all web sources as long as it is legally permissible. E.g. we currently don't track LinkedIn but that might change soon (link).