Yahoo will let users of its email, photo-sharing and other online products link their content and activities directly into Facebook.

"With this integration, we are opening the door for two of the Internet's largest online communities to make it easier for people to stay connected," said Jim Stoneham, vice president of Communities for Yahoo. "It also enables us to further the Yahoo Open Strategy, which is aimed at making experiences dramatically more open, social and personally relevant for the more than 500 million people that visit Yahoo! each month."

Yahoo's Facebook Connect integration will include Yahoo Mail and on properties like Yahoo News, Yaho! Sports, and Yahoo Finance. It will enable them to connect with Facebook friends on Yahoo, view a feed of their friends' related activity on Yahoo, and share content--such as photos from Flickr or comments on news stories--with all of their friends on Facebook. The content that consumers share with Facebook friends will then create a loop that drives visitors back to Yahoo.

This partnership extends the current Facebook integration on Yahoo which enables Facebook users to access their stream and update their status from the Yahoo homepage, provides "Share on Facebook" options across the Yahoo network, and allows Facebook to access Yahoo Contacts. People using both Yahoo and Facebook will soon be able to share updates across both networks.

The integration is expected to begin in the first half of 2010.

Wednesday's announcement takes the integration between Yahoo and Facebook a step further, by automatically pushing activities performed on Yahoo sites, such as photos shared on Yahoo's Flickr, into the Facebook news feed.

Facebook Connect, which was introduced last year, provides a universal ID that lets people automatically log on to participating sites with their Facebook credentials. It also allows people to notify their Facebook friends about their activities on third-party Web sites.