Flickr allows users to sign up for the Flickr Twitter Beta program, that allows them to link their Flickr and Twitter accounts (using Oauth) to send out a Tweet whenever they upload a new photo via email. To set up, visit this link, authorize your account, click "Head over to Twitter now" link, click "Allow" link. You'll be redirected back to Flickr. Open your address book on your mobile device and add your unique email+Twitter address. When you upload via email, the subject line will be taken as your Twitter tweet, and a special Flickr-y short URL to the photo will be appended.