I looked around for a tool to do this for about an hour last night. This was the best way I found because it can run in the background and if it gets interrupted, it will pick up where it left off. Just open up terminal and run the script.
“A Python script to grab all your photos from flickr and dump them into a directory, organized into folders by set name.
Original author is Colm MacCárthaigh.
Changes include tweaks to download full-size original images and improvements in handling UTF8 file and photoset names.
Run it like this:
python flickrtouchr.py FlickrBackupFolder
You’ll be prompted to authorize with Flickr, and then the magic happens.”