Foter is a Flickr search engine. You can filter by Commercial or Non-Commercial use and a few other options. There are no adds that i have found yet although the site says it is signed up to amazon. Make sure you check the license of an image before you use it.

This site has a nice feature, when you selct an image it will give you the attribution code ready for you to use to make your life easier and more likely to attribute an image properely.