We've always supported exporting calendars to listing sites via iCal. We've received a lot of recent requests to be able to do the opposite -- import bookings/blocked off time from other listing sites via iCal. Today, we released an update that adds two way sync support!
To set this up, you'll need to set up calendar import and export in each property. Export is already covered in our Hook up iCal availability calendars to update listing sites article.
For calendar import, go to the property Calendar Import section and add a calendar import using the iCal feed from your listing site, like VRBO, HomeAway, AirBNB, etc:
When you create the import for the first time, it'll do an initial pull of items from the calendar, then automatically update every few hours. You can view the last status in the log under the calendar import.
Currently, only AirBNB provides enough information in their iCal feeds for us to create bookings. If you want bookings with guest info and charges from other sites, you'll need to add that information by hand. For other feeds, go into the blocked off time and use the new "Convert to Booking" button to convert the block off to a booking.
If you have any ideas or find iCal feeds that we don't support, let us know and we'll look into it.