I get asked this question a lot. I used to collect baseball cards from the 1950s, 1960s and early 1970s but sold my extensive collection to help pay for graduate school. I know that when I was 6 and spending my entire allowance on baseball cards every week that I had no idea that my investment of $1 a week would pay for 1 entire year of graduate school. While those early collections have paid off nicely other collections are more for the sentimental value they bring. I leave the money making heavy lifting to the companies I help start and the technologies we develop. These days, I find myself a fan of old and rare books. Most people take books more or less for granted these days, but 100 years ago, or even 200 years ago, books were a rare and treasured item. I have a preference for two types of books, 1) “The Art of War” by Sun Tzu (I own almost every English translation in print) and 2) Rare 1860s English books on Chess. I find these 150 year old books to be VERY enjoyable. These leather bound masterpieces have simple and reliable strategies and are wonderful to own and read. My personal library contains over 300 modern volumes but less than a dozen really cherished rare books. In this increasingly digital age, it is hard to imagine the Kindle or the iPad being cherished 150 years from now… chances are the built in batteries will be dead by then.