My mom has a plant at her house, and everytime I visit, or if she comes to visit me, I come home with some real live catnip.

My two just love it.

Peanut, who is more wary of everything, sniffs it first, then proceeds to roll and roll and roll, then off to the couch for a good solid nap.

Tubby dives right in and rolls in it, then eats it, then proceeds to throw up an hour or two later, so he doesn't get it much anymore. Poor Tubby doesn't get much besides cat food anymore because of his failing kidneys. I used to bring Tubby with me when I visited my mom, and let him outside on a leash. He would immediately head for the catnip plant and roll around and eat to his heart's content. He'd then end up passed out, right in the middle of the squashed down plant. But catnip is like a weed and the very next day it would be back to normal and he'd have at it again.