This free tool will crawl an HTTPS-website (entire website, recursively, following internal links) and search for non-secure images, scripts and css-files that will trigger a warning message in browsers. The number of pages crawled is limited to 400 per website. The results are cached for 10 minutes.
As you might know Google has announced that going HTTPS will give you a minor ranking boost. Lots of folks rushed into buying SSL-certificates and switching to HTTPS. But after enabling SSL on your webserver - remember to test your pages for "absolute" URLs that point to unsecure content - images and scripts.
This page accepts hash-parameters like this: https://www.jitbit.com/sslcheck/#url=https://www.google.com/, feel free to use.