Most of the tasks that can be accomplished with Flickr's online managment tool Organizr can be done in offline mode with DFO. This includes managing your current photo sets, creating new ones, and editing tags and descriptions. For installation instructions on Ubuntu see here.
Linux users also have the option to use the program Kflickr to upload their photos hassle free to flickr. With Kflickr, you also need to authenticate yourself only once. The software will then remember your login information and download tag and set information for your account. Images can then be uploaded by dragging and dropping them to the Kflicker window. Kflickr is already included in various Linux distributions. The latest version can be downloaded here. For more information, see here.