Yammer is a “Twitter for the enterprise” platform that (to our dismay) won TechCrunch50 last year. A year later the enterprise microblogging space is growing rapidly and Yammer is still moving forward, along with competitors like Socialcast and Socialtext Signals. Today Yammer has announced a pair of Microsoft-centric additions that should be big for business users: an Outlook plug-in and a Windows Mobile app. Outlook is still huge in the enterprise, and a decent working integration with it should be an easier sell than any other kind of desktop access.

Any enterprise microblogging and messaging apps worth their salt have some kind of desktop app by this point. Most of them, including Yammer, have started out with Adobe AIR. The big advantage with AIR is that it’s cross-platform. But getting users to start using yet another app on their already cluttered desktop isn’t always successful.

With the Outlook plug-in, an extra pane is added alongside the other aspects to Outlook. Users can then message and reply to colleagues, upload attachments, and do basically everything that the AIR app does.

The fundamental difference is that the plug-in takes microblogging to where many enterprise users are already spending a lot of their time. A prime example is how users will be able to CC an email to either their whole Yammer network or to a specific group. As for the other app, Windows Mobile may not be quite as vital as Outlook but it still has a robust presence in the enterprise mobile market.

One of the persistent dilemmmas with standalone apps like Yammer is that (even with desktop and mobile apps) it is never easy to include it in preexisting workflows. It’s always harder to sell an enterprise app that doesn’t play nice with systems already in place. Integrating Yammer with two Microsoft products that continue to hold mind share in the enterprise world is a step towards solving this problem.