In reply to Justin Tadlock.

Unfortunately it doesn't work for all of them, blockquotes being the one I'd find most useful. But you can add alignleft or alignright manually. I also created a pair of custom styles, callout-left and callout-right, which I can apply to audio and video, tables and quotes and which (as the names imply) allow me to float items left or right and a consistent size. Next trick is to work out how to add a button so that I can add them from the toolbar (which is all the alignment options are doing, really).