Before, you could click on the Videos link in the menu bar of Google's home page to search for a video across multiple video services. Now, the YouTube link takes you directly to, you guessed it, YouTube. The Videos link was removed from Google's home page, but it still exists on the search results page.
To search across multiple video services, enter your search term and then from the search results page, you'll find the Videos link in the left-hand column. It will then display videos from multiple sources, including but not limited to YouTube. And if you scroll down a bit in the left-hand nav, you can select a specific source under the "Any source" header.