In one of the german Forums someone asked on how to add the name of the blog to a users name (or additional text) in Feeds. While looking up on how this could be done I decided to write a little Plugin. I called it Feedname.
It is a very small and new Plugin, therefore I have not uploaded it into the Wordpress Plugin Repository. Anyway, feel free to check it out and leave some Feedback on the Discussion Page (or even directly on this Page) in Codex if you like.
It is licensed unter GPL 3.0, the code is PHP version 5 and hopefully my english is good enough sothat you can handle the comments inside the code.