Flickr has been indicating integration with Twitter when it gave users option to add twitter account to Flickr profile. But now you can directly upload pictures to twitter from your flicker account.
You are sure gonna see a lot of http://flic.kr links on your twitter profile.
So here's how you add flickr2twitter
About Flickr Twitter Beta Info for setting up your Flickr Twitter
Step 1: www.flickr.com/account/blogs/add/twitter
You'll need to authorize your account. Click on the "Head over to Twitter now" link.
Step 2: Click on the "Allow" link.
Step 3: You'll be redirected back to Flickr. Open up your address book on your mobile device and add your unique email+Twitter address. (This is just your existing upload by email address with "2twitter" added.)
Step 4: Have at it. 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.