To perform the following trick go to Three Horns Valley and then northwest on the map to the hideout where you fight the Bad Maw boss (next to the entrance to Bloodshot Stronghold). Pick up the Eridium Mad Maw drops when you have defeated him and then go to the Bloodshot Stronghold and choose the 'Save and Quit' option. When you continue the game return to Three Horns Valley and defeat Bad Maw again to get more Eridium. This can be repeated as many times as desired.
Added by: Sanzano Sep 21st 2012, ID#4891