jcapshaw

Google released a new way to notify them of duplicate content so that it is not indexed and penalized. http://googlewebmastercentral.blogspot.com/2009/02/specify-your-canonical.html
This plugin allows for you to link to another post or your home page from each post or page that is written letting Google know it is duplicate content.
This is a stable version.

Duplicate Content Link

Allows you to tell Google, Yahoo, and MSN if another page is the canonical, real URL to avoid duplicate content penalties.

Sayfur Rahman

This plugin will enable post ticker in your wordpress theme. You can embed post ticker via shortcode in everywhere you want, even in theme files.
Wanna see how it works? Click here: http://bytecoder.info/plugin/

Bytecoder Post Ticker

Bytecoder Post Tickers is an awesome, super lightweight plugin for your wordpress website.

Duplicate Content Link vs Bytecoder Post Ticker