Another great way to learn more is with hands on labs. Here is a current list of Exchange 2003 Free online labs
It's simple: no complex setup or installation is required to try out Exchange Server 2003 running in the full-featured TechNet Virtual Lab. You get a downloadable manual and a 90-minute block of time for each module. You can sign up for additional 90-minute blocks any time.
More information and an updated list:
http://www.microsoft.com/technet/traincert/virtuallab/exchange.mspx
- Joel