Voki is a free online tool that allows users to create customized avatars, add voice recordings to the avatars, and share the avatars on blogs, websites and profiles. It can help present information and promote ideas in an engaging way. Users can create an account, design an avatar, and share it with others. While similar tools like Doppel Me allow avatar creation, Voki offers more customization options and the ability to add voice recordings to the avatars.