Evolver (currently in alpha) is an interesting service. It allows you to build a 3D avatar either from scratch and components or from a photograph of yourself, and export that avatar as an image, a functional 3D model in a couple of different formats (presently Maya [MA] or Kaydara 3D Data Exchange Format [FDX]), or a ready-made avatar for a number of 3D virtual environments.
They've got more planned it seems, like the ability to potentially embed a little animated 3D avatar in places where you might today be using a 2D image. Think Gravatars only in 3D.
