I'm writing an extension to send various contents from the web to the chromecast. If you are brave enough you can give it a try.
Update 0.8 (the new version is taking shape)
Major changes: new name. : )
To install the extension you have to drag and drop the crx file in the extensions tab (chrome://extensions)
If you use the stable channel of chrome, google will likely block the extension soon after the first restart of the browser. In that case, to use it further, I suggest installing chrome canary.
dropbox link: goo.gl/kgatdZ
PS: forgive my English