Download Winlibre or Maclibre based on your computer and install it. After installing select the open source apps you want and install. You can also re run these apps periodically to get the current versions of the installed apps.
Both of these apps are free and comes with cool apps like OpenOffice, VLC, Gimp etc. Winlibre is currently down because of lifehacker effect, but Maclibre is still live.
Winlibre comes with bundle of all the apps, or only winlibre program that downloads all the apps from the internet later.