The easiest way would be to use the Syndicate MOD here... http://www.snitzbitz.com/mods/details.asp?Version=All&mid=195

then include the JavaScript in the marquee example here... http://www.spiritjourney.co.uk/misc/marqueeexample.htm
(view source of that page to see how its done)

I know the above isn't ideal and rather crude, but I might have a proper look later to see if I can improve on that and use actual snitz code to try and generate a marquee from active topics unless someone else has already made something similar, as it something I would find useful too.<