Cool Websites play online

The Internet is an ocean of opportunities. Nowadays we can find a website or two for anything we need. But there are few who stand out from the crowd. Cool Websites is a collection of websites which provide value to users like us. Over the years I have come across so many useful/entertaining/interesting websites that are not known to many. They are not limited to any particular genre and in almost all aspects of our life, websites like these can be found. I have tried to curate a list of such websites.