LinkedIn has been for a long time the favourite social platform for professionals, part resume, part blog and part social media, it has a lot of desirable features. It's also undergoing a kind of renaissance for professionals looking to increase their profile and a very powerful tool for those who know how to wield it.
In my experience, it has a strong community of power users that make engaging on this platform much more appealing than the consumer-oriented social platforms. There is also resistance to content that is not strictly relevant to professional activities, so you'll see a lot less bullshit and politics than on FB or twitter and if you do, it's easier to ignore.
If you're not familiar with the platform, here's a good guide to get started and if you're primarily a B2B company, it's THE platform to invest in right now.