Flickr's introducing OpenID to make it faster and easier to sign-up for new accounts by letting you use one identity across multiple websites. So starting today, you'll be able to use a Google account to sign-up for a new Flickr account.
For existing Flickr account holders, you'll still need to sign in with your Yahoo! ID, but Flickr's rolling out a few new features to make signing in easier for you as well. You can now sign-in to your account without having to leave the page you were on, making it easier to post comments, favorite a photo or add someone as a new contact.
More Info: FAQ