Eclipse Phase
Your mind is software. Program it. Your body is a shell. Change it. Death is a disease. Cure it. Extinction is approaching. Fight it.
Posthuman Studios has released Eclipse Phase under a Creative Commons license. Writer and editor Rob Doyle hosts semi-official PDF versions of every core book for download at his blog. Feel free to grab them, check them out, and support Posthuman studios by purchasing print or digital copies when you decide to sink your teeth in!