hello, few days back i came around one site called the distrowatch . its a one of the place on the internet where you will be able to find most of the information about the various distributions of the linux, it includes various information like Distribution, link to the Home Page, Documentation, various Screenshots, info regarding the Download Mirrors, reviews and also the place from where you can buy the that Distro, and it also provide the various information regarding the previous versions of that OS as well.
And one of the best thing that i liked is that it is providing the list of top 100 Linux Distro according search made by the people and also it will show you the numbers rates [hits per day], so that you will be able to understand easily which one is in demand.
And over there they have provided something that is known as “Free Tech Guides“, where you will be able to find resources related to the Linux and all that, and also they provide various other important information related to Linux OS.
So have a look and have fun.