Since April 2014 Canal + has just put online a new version of its mobile application CanalPlay and provides compatibility with Chromecast Google.
The choice of several application for "caster" is already available
Here is a partial list chtite application that can run on the google key
Google Play Movies allowing buying and watching movies
Francetv Pluzz - Free: Watch FranceTV programs live or replay
All SFR TV SFR TV channel programs
Photo Cast for Chromecast. this app allows you to find photos on the screen
Red Bull TV videos, sports and action
CastOnTV that can send photos and videos on the screen of the TV, with music.
VEVO that lets you watch free music videos and live concerts
YoouKids: YouTube for our kids
Web Cast a Beta app for disseminating the content of the websites visited on the Chrome browser
TicTacToe for Chromecast a little more simple and basic game just nice to discover the possibilities offered by Chromecast key.