Yammer, one of our favorite enterprise microblogging tools, has been busy enhancing its services. There are two worthy items today: first is integration with On24’s webinar network, and the second is the ability to do work with Salesforce.com. Together they show how the company is trying its best to integrate with anyone and everyone it can to spread its reach.

On24 is one of the top-tier webcasting providers, and they have entered into a partnership with Yammer so that they can distribute content to external audiences. ON24 is also announcing a new feature to its Yammer application widget that supports Yammer External Networks, the public streams that aren’t tied to particular corporate domains. This enables employees to create separate private, secure networks for collaboration with groups outside their company, such as customers, partners and other third-party business contacts. The widget allows ON24 users to toggle between Yammer networks while attending webinars and other online events.

You can register for a complementary webcast (of course) here that goes into more details.

Yammer combined its APIs and Force.com to grab the activity stream information from within Salesforce, so that these objects can now be a part of the Yammer activity stream. What you didn’t know that Yammer had its own API? Here you go, and now you do. This integration happened through the help of Appirio, which we have written about before in joining Jive with Salesforce in April.

Now, those astute readers may realize that Salesforce has its own activity stream microblogging thing called Chatter, doesn’t this duplicate the function? Yes it does. But the bigger issue here is that Yammer is integrating things like crazy, before other software tools put their own activity streams inside their apps, just as Salesforce has done. Yammer is adding 200,000 customers a month, according to some press sources, and now stands at three million total customers, with half a million paid ones.