RevEye Reverse Image Search searches Google, Bing, Yandex, TinEye, and Baidu
Google Reverse Image Search, images.google.com (also available as Chrome and Firefox add-on), you can also right-click on the image.
INVID Verification Plugin download chrome ext put a link to a video in INVID, analyze thumbnails via TinEye, Yandex or Google reverse image search
Watchframebyframe.com watch youtube and Vimeo videos frame by frame
Dual Maps mashup of synchronized Google Maps, Aerial Imagery and Google Street View
Image Verification Assistant “features a multitude of image tampering detection algorithms plus metadata analysis, GPS Geolocation, EXIF Thumbnail extraction, and integration with reverse image search via Google.”
Jeffrey's Image Metadata Viewer might find photo metadata [won’t work on platforms like Facebook, they scrub metadata]. Here's an example of what you could find.
EXIF Quick View Chrome Extension
Crop and Search technique from Peter Adams at News Literacy Project
Sun Calc match the time of day a photo was taken. This example will walk you through a use case.
What to look at when investigating a YouTube Account
Storyful Video Archive search for verified user-generated videos by topic or keyword. You can search, but you have to pay to use the content.