Zynga and Yahoo! Inc have announced that Zynga will be bringing their set of social games to Yahoo!'s sites, in much the same way as they are available on Facebook and MySpace. The move means that Yahoo! users will be able to play Zynga games not only on Yahoo! websites but also via their email and instant messanger programs.

Heads were scratched after Zynga and Facebook tied up a five-year deal last week in the face of rumors about a rift in their business relationship, but those rumors now appear to have had some foundation following the announcement of a partnership with Yahoo! Inc.

Zynga is the biggest social gaming company on the block, with its flagship title FarmVille boasting over 80 million regular players on Facebook alone, making it the most used application on the site.

The company were quick to take advantage of Facebook's "Facebook Connect" scheme, encouraging websites and their visitors to use their Facebook credentials as a universal login around the internet.

However, for Zynga it meant that the company was able to further establish its identity apart from the pre-eminent social networking site.

Zynga also started introducing its own form of virtual currency to simplify in-game purchases for users. This conflicted with Facebook's own Facebook Credits scheme and was thought to be a source of problems between the two, as was the 30 percent commission that Facebook take from all Credits payments.

In common with Facebook, Yahoo has its own application platform, universal sign-in, and network update feed, allowing Zynga players to let their Yahoo! friends know what they're up to.