The Pixar Blog points to IMDb which lists Paul Eiding as a member of the cast list in WALL•E. Eiding is a voice actor and will be providing "additional voices" for the film.
The Pixar Blog also notes he has provided voice work for Cars, A Bug’s Life, Monster’s Inc. and Finding Nemo.
UPDATE: The Pixar Blog now points out that IMDb Pro lists Eiding as a cast member of Up (due for release in 2009), and again he will be providing "additional voices".
Last modified: March 16, 2008
“The Pixar Blog also notes he has provided voice work for every Pixar film except both Toy Story films, The Incredibles and Ratatouille. “
That’s excellent writing right there!