As the editor of The PCLinuxOS Magazine, I can vouch for the abilities of Scribus. We use it to publish our monthly magazine. It's a fine piece of software.
I'm not sure why this needs to be a Linux-specific article... nearly all of these tools (if not all of them) run on other platforms such as BSD, OS X, and Windows as well! That being said, this is a much appreciated list, since I know one day I'll want to do a book.
- Keyboard Shortcuts: