Most Downtown hotels offer free or fee-based wireless in their rooms or at least in common areas. Check with your hotel before arriving to confirm.
You'll find that many Internet cafés on Newbury Street and throughout the city offer free Wi-Fi. Most coffee shops, including branches of Pavement, Peets, Starbucks, and Espresso Royale, have free Wi-Fi available to customers. Others may charge a small fee (from $2 and up) depending on the minutes of usage.