I've been a Flickr pro user for 4 years, but the pro account costs 24,95\$/year and I was looking for something cheaper. Anyway I was thinking that after all, even if I don't renew my account, I can always access to all my pictures.... wrong! If you don't renew your pro Flickr account you can only access to the low resolution version of your own pictures. That's not acceptable for me, so I decided to download all my pictures and upload them somewhere else. Here comes the second disappointment: there is no automatic way to download all your pictures.
I simply had no time to write an application by myself, so I started searching on Google to see if there was something available to do this simple task. At the beginning I only found abandoned tools (closed source, the API was expired ecc...), paid tools, Windows only tools ecc... but finally I found this post http://hivelogic.com/articles/backing-up-flickr/
There is a Python script that automatically downloads all your Flickr pictures getting the highest resolution available, you can download the script from here https://github.com/dan/hivelogic-flickrtouchr
The usage is very simple
python flickrtouchr.py FlickrBackupFolder
A browser's window will be opened and you'll be prompted for authorization. After that, all you pictures will be downloaded.