This document provides an introduction to mobile learning, including: - An overview of the technologies used for mobile learning, such as PDAs, phones, MP3 players, and more. - A discussion of why mobile learning is needed, with an example of how radiology trainees benefit from portable learning tools. - A brief history of PDAs and their increasing capabilities from 1984 to present day. - Considerations for deploying mobile learning, including preparing materials, technical support needs, and challenges with evaluation. - Resources for further information on reports, books, and websites related to mobile and handheld learning.