Create a program that pulls the top posts from subreddits on Reddit and put it into a book then sell it. You could do this automatically by using Reddit's API and then using a library to convert the text into PDF, ePub, etc.
Hey that's not a half bad idea. One of the first things I do when I go to a new subreddit is check the top posts for month and year. I wish I could look at the top posts from the last 3 months sometime. If you had a service that just archived top posts month to month, removing duplicates then people could access that anytime. Don't know if I would charge for it initially but it's a cool service at least.