Microsoft Exchange Home Page
http://www.microsoft.com/exchange/default.mspx

What is Exchange Server?
http://www.microsoft.com/exchange/evaluation/whatis.mspx

History of Exchange
http://en.wikipedia.org/wiki/Microsoft_Exchange

Tech Target’s SearchExchange website
http://searchexchange.techtarget.com/

Exchange Solution Center
http://www.slipstick.com/

Microsoft Exchange Hosted Services by Microsoft®
http://www.microsoft.com/exchange/services/services.mspx

eNomia
Microsoft Hosted Exchange Services by eNomia
http://www.enomia.com/

LightEdge Solutions
Hosted Microsoft Exchange by LightEdge Solutions
http://www.lightedge.com/productsservices/it/exchange.html

Managed Exchange Services by Innotion Enterprises
http://www.innotion.com/managed_services.aspx

E-Mail Services – Exchange Hosting by Inet7
http://www.inet7.com/email_services/exchange_hosting.cfm