Web Ticker is a jQuery plugin that allows you to have items scrolling indefinitely across the screen. It uses some fancy calculations to ensure smooth continuous transitions.
jQuery Easy Ticker is a news ticker like plugin, which scrolls the list infinitely. It is highly customizable, flexible with lot of features and works in all browsers.
WebTicker is a simple jQuery ticker plugin. It can be use as a news ticker too.
It's free to use and it has some options for customizing.