What to do when you're making bags of money, and life's no fun anymore?
Follow the path of many imminent scientists and artists of our time and investigate the wonderful world of psychedelics. First, check out Erowid and deoxy.org. Have a read around until you find the types of experiences that sound like the most fun or most interesting. Read up on that substance (or combination of substances), being on the lookout for book recommendations to arm your mind before engaging in these experiences. Make sure you read Fear and Loathing in Las Vegas.
Magic Mushrooms are legal in many countries and are a great start. After that, morning glory (LSD) is a great mindbender, and I must recommend entering the K-Hole. But why stop there? There's still Peyote, Datura, Ayahuasca, Amanita Muscaria, Kava, Ibogaine, Salvia Divinorum, and that's before we even start to look at the synthetic breed, or substances found whilst in other dimensions!