Academic and Industrial Research
  2001 - Partitioning digital worlds
  2003 - Effects of visual separation and physical discontinuities when distributing information across multiple devices
  2003 - Toward characterizing the productivity benefits of very large displays
  2004 - Comparisons between Single Monitor and Multiple Monitor Users
  2004 - Wideband displays
  2005 - Distributed Display Environments Workshop
  2005 - mudibo

News Articles
  Study Reveals Multiple Monitors Increases Productivity
  Double the Fun with Multiple Monitors (Mac OS X)
  Multiple Monitors vs. Your Application: Assume one monitor, go to jail...

Blog entries
  A wonderful world of multiple monitors
  Multiple-Monitors are love
  Multiple Monitors and Productivity
  Seeing Double: An Unbiased View on the Benefits of Multiple Monitors
  Multiple Monitors rule

Forums and other discussions
  Realtime Soft
  Slashdot

Interfaces
  UltraMon
  Vern

Graphics Cards
  Appian
  ATI
  Matrox
  nVIDIA

Monitors
  9X Media
  Digital Tigers
  go-l

Mobile Computing
  Estari

Stands and Mounting Brackets
  ErgoMounts
  Ergotron
  LCDMonitorArm.com

Mac OS X
  Double the Fun with Multiple Monitors

Microsoft Windows
  Using Multiple Monitors with Windows XP
  Multiple Monitors Overview
  (video) How to Set Up Multiple Monitors

Linux, UNIX, X-Windows, etc.
  Multiple Monitors with X Mini Guide
  HOWTO Dual Monitors
  Walkthrough: 3 monitors with two video cards using Mandriva Linux 2005 Club Edition

Sun
  Multiple Monitors on a System

Other resources pages
  Realtime Soft
  MultipleMonitors.Org
  BuildOrBuy