Way back when, I used to use the Firefox plugin DownThemAll with the AntiContainer add-on to save images from websites to my own collection. The advantage of this setup was it worked within the browser to automatically identify images you wanted to save and then go out and grab those images from the hosting sites directly. Websites often have images hosted on "container" pages so you can't just save the link to the image otherwise you end up saving an HTML file. The AntiContainer add-on let you create an XML configuration file for each image hosting site (and DownThemAll created a whole bunch of them for you) that tells DownThemAll how to grab the actual image in the container page.
I am looking to see if anyone knows of any similar image downloader (preferably a browser plug-in) that allows you to create your own custom capture scheme without relying on the developer to do it for you.