If it's going to take a while to get your infrastructure up and running or even migrated to Exchange 2003 - Dave at http://geekswithblogs.net/wallabyfan/archive/2006/04/25/76292.aspx and Gears at CoolSmartphone http://www.coolsmartphone.com/index.php?option=articles&task=viewarticle&artid=668&Itemid=3 have found a really simple way of getting a POC up and running in minutes!

It's based around using the Mail2Web service and they have now enabled SP2 and Push Email for their hosted offering:

http://services.mail2web.com/Business/Exchange/SP2features.asp

So when your boss says - can we get this up and running quickly...... this is an easy way of doing so!