Back To School
In my neighbourhood, the kids head back to school next week, and the fall session has already started in other school districts. Maybe you've thought about taking a few courses yourself, but don't have the time or energy to get to evening classes, or there's no school nearby.
If it's just the experience that you're looking for, and not the credits, you can attend courses online at a few major universities. There are no fees, and courses are stored online so you can listen to them on demand.
For example, Berkeley has a broad range of courses, with podcasts and webcasts that you can access. To help you remember to attend, you can subscribe to the RSS feed of any event or course. Maybe I'll do the Introduction to Statistics, to brush up on those long forgotten skills.
Or the Modern Poetry course at Open Yale Courses might be an easier place to start.