Berimbau: Article by Richard P. Graham and N. Scott Robinson covering history, popular and traditional Brazilian use, and recent developments.
Capoeirista.com: Berimbau: Photograph, description, and audio samples of the capoeira rhythms. [English/Portuguese]
DrumsOnTheWeb.com: Frank Colon's Informal Lesson: Introduction to playing the berimbau.
Rhythmweb: The Brazilian Berimbau: Description and illustration, with links.
The Art of Building the Berimbau: Covers traditional and modern materials and methods.