Twitter has added the ReTweet (RT) feature in their web interface.
The below screen is appearing in Twitter after getting loged in.
It seems this feature in still in Beta only. And it is available only for some users only.
Just I assume that currently Twitter is providing this feature only for the users whose followers count is greater than following count. But I am not sure about it. If you know more about it you can share it thro' comments.
It is showing new icon for identifying reweets.
It seems some people are not satisfied with this feature, still they are willing to use third-party applications only.