How to install Owncloud on your Linux Box

A lot of people use cloud storage systems like Dropbox, Spideroak or Ubuntu One, these software allow you to store your files on a remote server (on the clouds) and be able to access them on all your devices: computers with Linux,mac or Windows and also from tablets and smarthphones.
But it wouldn’t better to manage yourself your own storage system ?

This could be really useful for small and large company to setup their own storage with their security policy and permission systems, or also for people that want to have the full control on their files.