Aging web giant Yahoo and leading social game developer Zynga have announced a new partnership this morning, that “weaves the web’s most Popular social games throughout yahoo!” — or will in the coming months as Zynga games roll out. It’s not clear which games will be available through Yahoo, or how they’ll be available to users.

Those who have been following Zynga’s contentious relationship with Facebook lately will likely assume that this is another move by the developer to find more distribution, users and revenue beyond Facebook. And that’s true. Zynga tells us that Credits, Facebook’s virtual currency for its platform, that includes a 30% fee and will somehow be mandatory, will not be appearing in the Yahoo implementations. Meanwhile, Zynga has also been subtly directing users of its hit Facebook app, FarmVille, to go use the web site version — a possible way for Zynga to maintain more control over players regardless of what happens with Facebook.

But there are other reasons to not read too much into today’s announcement, besides the fact that Zynga and Facebook recently announced a five-year partnership. Zynga has already been busy making partnerships with other developers, most notably with Microsoft’s MSN Games portal in February.

It makes sense for Zynga to want to diversify, regardless of its relationship with Facebook. Yahoo, like Microsoft, likely has some users who would like to play Zynga’s games but are not on Facebook. Interestingly, it appears the Yahoo deal has been in the works for some time, and was only recently finalized. From AllThingsD’s Kara Swisher:

BoomTown actually called Zynga CEO Mark Pincus and asked him specifically about this deal last week and he denied it completely, noting the pair had been in discussions “forever” and that “it’s impossible to get anything done with that company.”

Here’s some more detail about the deal, from the press release.