Not sure if I've already bookmarked another page from this site. It's a repository of European heritage, which for us means sources and images. I think it will become quite a massive repository of sources for all periods and regions of Europe.
Yes, it is a great project. If you are interested, here are some ideas how to start working with the collections in the classroom: http://geschichtsunterricht.wordpress.com/2014/02/01/working-with-the-europeana-1914-18-collections-in-the-history-classroom-part-13-scarcity-vs-abundance/