How can I make particles collide with each other? Is this possible? If it is, how can it be done?

Thanks in advance!

EDIT: Here's a quick sample file I made: DOWNLOAD SAMPLE

Notice the particles merge in with each other, instead of bouncing off of each other. I want them to behave like marbles would if they were dumped into a cup. They'd bounce, settle, and create a pile within the cup.
There is an Add-on called Molecular. It makes the particles act as Rigid Bodies. The particles can be linked to each other as well.

Here is a teaser trailer that the coder made.

Just download the .zip, go to File > User Preferences > Addons and click Install from File. Select the .zip. Check it to enable it. If you need more help installing, let me know.