LinkedIn isn't just a place for personal promotion and career networking — businesses can do a lot on the professional network. In Dan Sherman's Maximum Success With LinkedIn, that point is stressed heavily.
LinkedIn looks a lot like Facebook, but with a targeted audience that companies can take advantage of. The best part: many of the solutions for increasing the presence of your business on LinkedIn are free and easy to use.
And many of them you are probably already doing in other social media, just not on LinkedIn.