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