From WordPress.com: Tips on formatting poetry for your blog. First, I can’t believe that there has been no improvement on that tedious “@nbsp;” code, or the “pre” code that changes your font to courier. What’s up with that?
Nevertheless, I think that the section on line breaks can be helpful:
If you hit the Return key in the Visual Editor, you’ll probably notice a lot of extra space between the previous line and the new one. That’s because whether you hit the Return key one time or twelve, the Visual Editor will interpret that to mean that you want to start a new paragraph.
But sometimes you don’t want to create a new paragraph, and want to start a new line instead. You can begin a new line by pressing Shift+Return.
The next line after the line break will start immediately below the previous one, with no extra white space, so you can easily create clearly defined blocks of verse inside your poem.
You can add as many line breaks as you want; the Visual Editor will never ignore them. Each time you hit Shift+Return, you’ll get an extra empty line, so you can also use this technique to add really big sections of white space to your poems.