There are a number of repositories out there that only store open content so a search of that site will always return openly licensed content. You can find a list of some of the repositories here.
There are also lots of non site specific search engines out there and some are integrating a search facility that provides the capability to search on licence. The biggest of these is Google, there are other search engines like Xpert, from Nottingham University, that aggregate a search across a number of open databases. In addition you have search engines in non exclusively open repositories like YouTuube and Flickr that allow you to search on licence.
sidebar left, keeps IE7 block border rendering happy, this must be the last (bottom-most) block in stack
