If it's adventure you seek, check out Presidential Airways. They operate Casa's. This is all google would turn up....
http://www.blackwaterusa.com/aviation/aircharter.asp
Also there is some operator that bought alot of military C12's and operates them in interesting places, or mundane dropping sterile fruit flys in SoCal. I flew with a cat that worked there. I forget the name of the outfit though....
Good luck....