Fire Universal Uploader is a Firefox extension that lets you upload and also download videos, pictures, documents and other files to the above websites from a common interface.
Getting started is simple - click the dropbox icon in the Firefox status bar, select one of service where you wish to upload the file(s) and then drag-n-drop the pictures or videos - you content will be online almost the next minute.
The Universal Uploader is like a two-way FTP client for YouTube, Flickr and other sites - you can browse stuff that's already available in your account or upload new media file. The upcoming version could have support for Google Video, Photobucket and more.
To download the file uploader, visit addons.mozilla.org. In case of Flickr and Picasaweb, you'll have to authorize the service before uploading pictures the first time.
For some reason, the official Flickr batch uploader software never worked on my Windows machine and this Firefox uploader is like a god-send - more usable than the web based file uploaders.
Related: Use Email to Upload Videos on YouTube