Some manufacturers are trying to solve the small keyboard problem by replacing the keyboard with an electronic pen. However, these pen-based devices rely on handwriting recognition technologies, which are still in their infancy.

PDA Overview 
Outlines the history, evolution and technologies behind the PDA. Includes graphics, diagrams and an integrated glossary.

BYTE magazine article on rugged hand-held computers
Provides information on evaluating the ruggedness of a hand-held computer.