And you can post about things you are selling. Do you make these items? Then write about the process. Are you a professional real estate agent? then post about the services you provide. A lawyer? then again, post about your special services. A carpenter, gardener, plumber, electrician? You can write about what you do for your clients. Do you have a local store? Post about your products (remember to include the city where you are). Do you have a restaurant? Tell people about your menu and how the foods are prepared.
Take a look at the TOS to see how you fit in with the restrictions on WordPress.com: