While this site is still in its beta testing state and may not always operate correctly, I believe it's worth listing here for its vast resources and potential as a great place to start your European Genealogy research. Rather than paraphrase what the site is all about I have included a quote from their "About Us" page.
"Europeana.eu is about ideas and inspiration. It links you to 2 million digital items.
* Images - paintings, drawings, maps, photos and pictures of museum objects
* Texts - books, newspapers, letters, diaries and archival papers
* Sounds - music and spoken word from cylinders, tapes, discs and radio broadcasts
* Videos - films, newsreels and TV broadcasts
Some of these are world famous, others are hidden treasures from Europe's
* museums and galleries
* audio-visual collections"
When this is fully functional, this is going to be at the top of my list of great places to do research. Fair warning, some of the archives are in the native language of the country of origin, so you may need an interpreter for those that are not in English. Check it out: