Linux has already made a name for itself in the OS market. What i like about it is that its very easy to get hold of, easy to install, it takes into account facts like you may want to try it before u let it replace your favourite operating system (try knoppix). It has already found its ways into nooks and cranies like mobile devices, watches, gaming consoles like xbox / playstation and what not.
However, if you have missed the wave (been left behind), now would be a good point to start. Here's a nice site called Tinyminds which has a lot of stuff that you can use to get started. Of course, the official place for linux documentation (The Linux documentation project or TLDP for short) is also a good reference site.
If you have already heard of linux, then you will have also heard of names like Redhat, Fedora, Mandrake, Suse, Debian, etc. These are all distributions of linux (or distro's for short). If you are wondering which one to pick or already have a linux running and curious about others - distrowatch might be a good place to keep tabs on.