Research in Motion has officially released BlackBerry Enterprise Server Express.  BES Express is a FREE version of BlackBerry Enterprise Server intended for  small and medium sized businesses, although RIM will tell BES Express is intended for businesses of all sizes.

BlackBerry® Enterprise Server Express enables businesses of any size to quickly and easily get started with the BlackBerry solution. It provides advanced BlackBerry smartphone features with no additional software or user license fees, and works with any Internet-enabled BlackBerry data plan or a BlackBerry enterprise data plan.

BlackBerry Enterprise Server Express runs on Microsoft Exchange and Windows Small Business Server.  It is a free download and you can get it from the link below.

Download:  BlackBerry Enterprise Server Express