My Collection of Flickr Tools:
Flickr Uploadr: When I was getting everything up to Flickr initially, I used the flickr uploadr at the top of this page: http://flickr.com/tools/
FlickrDown: I've always gone back to this program to download photos quickly, because I like the interface. But it does not have a real easy way to backup all your photos. It was designed to backup your sets, but if some of your photos are not in a set, they don't get downloaded: http://www.greggman.com/pages/flickrdown.htm
So I started using FlickrEdit to download all the photos at once. It has a "backup" feature as well that apparently keeps track of all of your photos and can tell if more were uploaded to Flickr since the last backup. I am not confident that it got all of my photos just because I have over 10,000, but once I get all of the photos in sync, it will be a lot easier to keep up with it: http://sunkencity.org/flickredit