Producttimelines.com

"The intent of this site is to provide a reference (for product managers, developers, designers, VCs, and anyone else who geeks out on products) about what successful products have looked like, both at launch and beyond."

I found it very iteresting to see timeline of this big companies and their milestones. It could be also very usefull to find out some corellations between rival companies. I hope they will add more products for example YT, Google and Steemit of course :)