With this Flickr PHP library by Phan Thanh Cong that access the flickr API, users can upload images to Imgur, Imageshack, Picasa, Flickr, and Postimage. The author aims to ease the uploading process with the PHP remote uploader. Free and paid versions available. Also accessible instructions to transfer images from one single point.
The lemonwhale API comes as a two part REST API that features JSON: one public and one private, each with separate endpoints. The public one downloads public information about videos. The private API is for altering your videos, like changing the title, or creating a new live broadcast. Authentication is required for the private API.
If you wonder which of the 267 APIs on this site people view most often you might be surprised. It's not Google Maps, it's YouTube. Which has been true for quite some time. But the number of mashups using YouTube has been small, until recently when they've started to pick-up.