LinkedIn is a professional network as its tag line shows "World's Largest Professional Network". Even some people are using it for advertising as well. You can start a discussion in LinkedIn regarding your product or service, send mail to relevant members.
I did not use this site to much. Just made a profile and added some friends.
Still I hear that it is a great way to advertise your products there.
Any success campaign on that site? What did you do?
Linkedin advertising is pretty expensive, I normally A/B test an advert somewhere like Facebook before running the ad on Linkedin. Minimum spend on LI is much higher than elsewhere, that being said if you need to target your product by job title it's pretty much your only option.