iCalParse is a Windows Mobile app for importing iCalendar appointments/tasks.

Features:
- Import appointments/tasks direct from iCal files (*.icl, *.ics). It is also possible to chose which appointments/tasks should be imported and which not.
- Enables support for more features than the original Windows Mobile calendar has. eg. Recurrence Dates or Exclusion Dates.
- Make a quick look at the appointments/tasks stored in the iCal files.
- Replace all appointments/tasks on the device with appointments/tasks stored in an iCal file.
- Filtering of Tasks/Appointments vUpdate old and add new appointments/tasks from an iCal file.
- Delete all appointments/tasks stored on the device.
- Export all appointments stored an the device to an iCalendar file. Export all tasks stored on the device to an iCalendar file.
- Encrypt private informations.
- Timezone support.
- Customize calendar informations
- Define custom categories for the imported appointments/tasks.
- Remove HTML/CSS tags from the description of the appointments.
- Enhanced possibilities to replace strings which are added to the appointments/tasks automatically from the PIM Application with custom ones.
- Load and Parse ICal files direct from the Internet. (HTTP/HTTPS/WEBCAL/WEBCALS/CALDAV) .icl and .ics files are associated to the program.
- Auto syncing Logging
- Commandline Options Fingerfriendly landscape/portrait mode aware GUI
- CALDAV support for two way synchronization
- Two way synchronzation
- Usage statistics

The CALDAV feature was confirmed to work with:

Google calendar
Hint: The url for your google calendar has the following format [ https://www.google.com/calendar/dav/ [ your Google Calendar ID ] /events/ ].

Your Google Calendar ID for your primary calendar is just your email address, but for all other calendars the Calendar ID will be in the form of [ long string of characters]@group.calendar.google.com. You can get the Calendar ID by clicking the down arrow next to your calendar at calendar.google.com and selecting 'Calendar Settings'. Be sure to use https in your URL, as an http address will not work.

DAViCal
hint: The url for your DAViCal calendar has the following format [ [url]https://[yourDomain]/caldav.php/caldav/home/ ]

sabredav
hint: The url for your sabredav calendar has the following format [ [url]http://[yourDomain]/sabredav/calendarserver.php/calendars/[yourUsername]/default/ ]

MobileMe (currently only one way sync because apple made some chances to limit third party apps)
hint: For MobileMe you need an url similar to the following to sync with your calendar. webcal://www.me.com/ca/sharesubscribe/1.287005891/M2CD-1-2-0AD73313-EB67-4AEA-B558-A1551FAB2453.ics Here you can find a step by step desciption from apple how to create such an url. You have to use the "To share a calendar publicly" description and just type in your e-mail address so you get the url. http://help.apple.com/mobileme/interface/index.html?lang=en#mm6b1a9479