Flickr did not tell that they have a new service to post your photos to Twitter from Flickr directly. If you have both Flickr and Twitter account, just login to Flickr and follow this link (http://www.flickr.com/account/blogs/add/twitter) and allow Flickr service in your Twitter account. Then Flickr will give you the email address to you that you can sent to Twitter. Attach the photo in your email and sent to the email address provided by Flickr.
via: Digital Insipiration