A new feature in the personal feed aggregator FriendFeed lets users reply to Twitter posts that show up on the service, and have those replies posted to Twitter itself. Previously, what happened in FriendFeed stayed in FriendFeed.
You can only reply to Twitter posts in FriendFeed. Your post will start @(username), which is the standard for a reply on Twitter. You can't create a new Twitter item without the reply text. So FriendFeed is still not the new Twitter.
FriendFeed in reverse now exists, by the way: Ping.fm, a service that sends items to multiple microblog services at once.
Another Twitter helper in the news today: Quotably threads Twitter chat.