10 years of OWA
On May 23, 1997 Microsoft released Exchange Server 5.0, which contained a Web based e-mail interface called "Exchange Web Access". Later on, this web interface changed its name to Outlook Web Access and was significantly improved.
For a list of the great features of Exchange 2007 OWA, please read Client Features in Outlook Web Access.
Bharat Suneja, a Exchange MVP has written a great post about this subject that even includes a screenshot from the former Exchange Web Access: Happy Birthday OWA: Outlook Web Access Turns 10!