A site I have been working on has had a Flash banner with scrolling text for a couple of years. The problem is that the page took longer than it should have to load, and visitors couldn’t see the banner at all (company logo etc.) if they didn’t have a flash plugin.
Other than that the original script was used: http://www.users.globalnet.co.uk/~thompp/jsscripts/t_newsticker.html
My version is at http://www.chocolatehedgehog.co.uk/files/jsnewsticker.txt