"DropDAV lets you access Dropbox without the Dropbox app. It stands between the Dropbox API and WebDAV clients, giving your Dropbox a seamless WebDAV interface. It was developed specifically for use with Apple's iWork suite for iPad, and works smoothly with every other WebDAV client. Use DropDAV anywhere a WebDAV server is supported and add more uses to the most useful file service in the world."
DAV-pocket is now being used by many Google Docs users with applications which support WebDAV. The most popular application is Pages for iPad - word processing app on Apple's iPad. Here's a step-by-step guide to integrate your Pages for iPad with Google Docs.
ownCloud gives you universal access to your files through a web interface or WebDAV. It also provides a platform to easily view & sync your contacts, calendars and bookmarks across all your devices and enables basic editing right on the web. Installation has minimal server requirements, doesn't need special permissions and is quick. ownCloud is extendable via a simple but powerful API for applications and plugins.