I have accomplished this (getting a nice printout of everything currently displayed in the main content column) by using a @media print-only CSS stylesheet tiddler setting display:none on all the "user chrome" elements (nav menus, borders) I want to hide, changing the fonts (non-serif on headers, serif on body) etc. I highly recommend Firefox+Firebug for getting DOM element details.
Unfortunately I've lost my main computer and haven't yet gotten everything restored to the point where I could post specific examples, but hope this helps get you started in the meantime.