I was searching for easy cloud service recently. My findings were less then satisfactory - just client applications, no WebDAV support or high prices. Then I found ownCloud.
It has couple of strong points:
- Open source, PHP based so it can be hosted without any special requirements
- Easy, clean and configurable interface
- WebDAV support for file management
- CalDAV support for calendar synchronization (although I got problems with Journal entries)
- CardDAV support for contacts synchronization