If you're not really interested in picking up any new skills, offer the ones you do have. Chances are, you can use whatever job or life skills you've already learned and apply them to the place you end up choosing to go.
This is especially true if you've worked as a teacher or carpenter, as many volunteer positions revolve around both of those jobs [source: Schaler]. Are you experienced in manual labor? You shouldn't have any trouble finding places around the world where you're needed. You might have more to offer than you ever realized -- being able to work in all types of weather can be important. Knowledge of how to run a business is a sought-after skill. Even animal tracking can be of benefit to some communities. There are volunteer positions available worldwide for nearly every skill-set, so chances are your profession or hobby can help an organization.