Now when you search Google Patents you'll be querying a database that includes European patents. Even more useful perhaps is Google's just-introduced attempt to find "prior art". Here's a description of the process from the Google Inside Search blog:
The Prior Art Finder identifies key phrases from the text of the patent, combines them into a search query, and displays relevant results from Google Patents, Google Scholar, Google Books, and the rest of the web. You’ll start to see the blue “Find prior art” button on individual patent pages starting today.
A prior art search produces Google's pick of the "Top Ten Results" and a sidebar menu of search terms used, with the option to include further suggested terms or your own chosen search terms to improve the result.
As usual, it's easier to grasp what's involved by looking for yourself, so Google's provided a typical search accessible via this link.
Note that Google's ability to make European patents available depends a lot on their skill at translation. In this respect they've been working with the European Patent Office to improve machine translation of technical documents.