I see a lot of people selling beanie babies at flea markets. This actually seems like a pretty bad way to sell them. Beanie babies are not nearly as popular as they used to be and at any given flea market you are only going to have a handful of customers who are really interested in buying them. Those buyers are probably not interested in buying the rarer or more high dollar babies.
It is much easier and more lucrative to sell online. You are not limited by the market available in your geography. You can sell to the entire world.