Start with http://css.maxdesign.com.au/listamatic/horizontal01.htm and tweak from there. My css-fu is rather weak but a bit of Googling should get you the rest of the way.

Don't get me wrong, I like your horizontal layout better than the `<br>`'s that devise puts in there. I just think this is something that should be able to be done a bit more cleanly, both in the view and the HTML/display separation.