Flickr allows users to download full res images, but it's a tedious multi-click process. It's pretty clear from reading the help forums that Flickr/Yahoo discourages distribution of full res images using Flickr, so they make the process as painful as possible.
GMAN: FlickrDown to the rescue. This open source free app is downloading my SIL's (sister-in-law) photoset as I type, I'll dump them in iPhoto later today. There's a similar open source app for OS X apparently, but my son is occupying the iMac at the moment. This one seems quite fine.