Many of us have skills or hobbies that we wish we'd picked up but never got around to. Now's your chance. Want to learn how to play the guitar? Use the Internet to research your ancestry? Ballroom dance? Many of these skills can be learned in classes held at community schools and colleges. Depending on the type of class you take and how often they're offered, these classes are usually inexpensive. Some schools offer courses specifically for senior citizens.
If your local community school doesn't offer anything that catches your interest, keep looking. Hobby and craft stores conduct free or inexpensive classes in knitting, scrapbooking and jewelry making. If you're interested in home improvement, those types of stores often have classes in everything from gardening to tiling your bathroom floor. Cooking classes and demonstrations are often held in kitchenware stores. You get the idea -- if you're interested in learning about it, chances are you can find a class in it.
Maybe you don't want to learn how to do anything, but you're interested in starting a collection. Whether you want to collect autographs or antique dolls, there are plenty of online groups and forums dedicated to your new hobby. Some of them meet in person or even hold conventions. No matter what your interest, you can find others out there with whom to discuss it.