There are many people out there who build from virtual bricks. The feeling is different but it has some pros: you never run out of bricks and spend less time searching for that brick too.
If you would like to design your model on a computer you can choose from several programs. Nevertheless, the alpha and omega is Lego Digital Designer (LDD), the official free designer tootl from the Lego Group. It has many advantages but its biggest limitation was that the available bricks and colors were very limited. Not any more.
Many LDD fans were already suspicious that LDD knows many more bricks and colors than available in one of the DesignByMe, Mindstorsm or Creator modes. Now with Lego's blessings the activation instructions has been published.
The new mode is called Universe Mode. The image below shows the bricks available before and after. The new mode does not show separate colors because there are so many bricks:
Detailed instructions are available here. It disallows me explicitly to include it here but it's all very easy, just a one line change in a config file. (Source: Eurobricks.)
Technic fans have started building immediately - this is an offroad car from parts never seen before in LDD:
Creations built in Universe mode cannot be ordered in the online shop of Lego but I hope that is not an issue for anyone. One excuse less why not start building right away!