FlickrCash searches for photos on Flickr in the most efficient way, so that you can see as many thumbnails as will fit in your browser. It loads up to 10 pages in the background, so it's very fast to browse through to find the photo you need.
It's got some cool features, like a preview that pops up when you click a thumbnail, listing all the sizes that are available for that photo. If you sign up and create an account (for free), you can save your search results, and put together a "shareable lightbox" of photos with a secret URL. This way you can search for some photos and share them with your clients in order to get their feedback. For example, check out my Sunset Lightbox. This makes it really easy to use Flickr to find stock photography, whether for your print projects, blog posts, presentations, or just for fun.
Before I even had a chance to blog about FlickrCash, Lifehacker beat me to it. There's also a Youtube video you can check out that demos all the features I mentioned and more: