I’ve posted a code snippet I used to sideload images from Flickr into WordPress, specifically for http://foodirl.com/ I originally stored all of my images on Flickr because I started the blog on Tumblr, knowing that I would move it later (which I did, to Crowd Fusion and then to WordPress).
Stick it in
mu-plugins and then load
wp-admin/?do_flickr_sideload. It doesn’t have lots of error checking, but it worked flawlessly for FoodIRL’s 160+ posts.