Twitpictoflickr.com is a site which provides free service to transfer your twitter pictures to flickr within few seconds. It dosen't ask you for your twitter or flickr password or any information other than user name.
1. Go to twitpictoflickr.com a screen will appear asking for your email address insert your flickr account email address and click on 'Next Step'
2. Second screen will ask you for your twitter/twitpic user name insert your twitter/twitpic user name and check the below box (as shown in image) and click on 'Next step'
3. A login screen will appear from flickr login to your account and click on 'OK I'LL AUTHORIZE IT'
and now check all your twitter pic are in flickr.