If you're looking for a way to sync your Windows Mobile calendar to Windows
PCs running a smaller/lighter/simpler calendar than Outlook, check out
BirdieSync, which works with Mozilla Sunbird:
http://calendarswamp.blogspot.com/2008/03/birdiesync-works-deleting-outlook-2003.html
Sunbird itself now can publish calendar feeds to Outlook and lots of other
calendars, including Apple iCal, thanks to a new service called Calgoo:
http://www.calgoo.com
Scott Mace