Multi-Monitor Productivity

Does having more then on computer monitor increase productivity?

Some research I did on the subject found:

• http://research.microsoft.com/displayArticle.aspx?id=433
• http://lifehacker.com/software/dual-monitor/dual-monitors-increase-productivity-168488.php
• http://www.matrox.com/graphics/en/gxm/products/dh2go/home.php

Vedors

Hardware

• http://digitaltigers.com/index.shtml?gclid=CJv0uqGo6I8CFR7qYAodNR8dkA
• http://www.9xmedia.com

Software

• http://www.mediachance.com/free/multimon.htm
• www.realtimesoft.com/ultramon

Hardware/Software Combo

• http://www.maxivista.com