Via Google Blogoscoped, you can now filter web pages on Google by license:

1. Web pages that aren’t filtered by license – the default option. This searches every page in the Google index.
2. Web pages that allow some forms of re-use – Creative Commons licenses.
3. Web pages that can be freely modified, adapted or built upon – Pretty much public domain.

Sounds like a fantastic feature. It’d be especially useful with image search; finding public domain or Creative Commons images can be a pain although Yotophoto can do a pretty good job.

Yahoo! launched a Creative Commons search engine earlier this year.