SMIL is based on the eXtensible Markup Language (XML). Rather than defining the actual formats used to represent multimedia data, it defines the commands that specify whether the various multimedia components should be played together or in sequence.

G2 Introduction: RealNetworks' Next Streaming Technology
TechWeb article (June 1998) by Leah Goldberg describing key improvements in RealNetworks' latest streaming-media technology, with sections on SMIL, bandwidth negotiation, and code examples.

SMIL Activity Statement
W3C activity statement for Synchronized Multimedia. Contains information on requirements, products and tools, and current drafts, press releases, articles and presentations.

SMIL Hopes to Weave the Streams
Wired article (November, 1997) about SMIL.

Synchronized Multimedia on the Web
Excellent tutorial explaining some neat tricks.

W3C's Audio, Video, and Synchronized Multimedia Page
Offers the latest news about SMIL as well as overviews, related links, publications, and discussion forums.