In general, yes, LinkedIn is a good professional networking tool. The population of LinkedIn is almost entirely professional, covers most industries and functions, and is worldwide, making it a potentially rich source for business contacts. It is not a panacea for companies looking for talent nor candidates looking for work, but at this point it is one of those places where you probably can't afford not to be if you are looking or want to be found.

Companies are increasingly using LinkedIn as a job sourcing tool. They will post positions and use LinkedIn's search capabilities to find "passive" candidates. Given the proliferation of job sites out there, LinkedIn has turned out to be a concentration point for talent and is thus in many ways more efficient for searching. Of course the issues with many "passive" candidates is that they want to stay passive - that is, they are quite happy where they are and have no interest in leaving. Recruiters burn a lot of hours and days calling passive candidates, but at least you can find them via LinkedIn.

Candidates have nothing to lose and everything to gain by being on LinkedIn, but it doesn't guarantee employment. I recommend any professional, whether employed or not, create a LinkedIn profile with the same effort, creativity and thought that you would put in to your resume. It is a resume of sorts, after all. And these days I find the first place I and many people I know, go to research both clients and candidates is LinkedIn. Without question, given the use of LinkedIn by in-house and outside recruiters as well as entrepreneurs and others in your function, you will greatly improve your chances of being "discovered" if you keep a profile here.

We get requests to join other networks all the time - just Google "professional networking sites" and you will find a number of them. However, most of the links are about LinkedIn for a good reason, it is the 800 pound gorilla of professional networking. There are many others including general purpose professional networking sites like Spoke, Jigsaw and Ryze, industry or function-specific sites such as Sermo, InMobile and ExpertCEO, or even social networking sites such as MySpace, Facebook and Friendster. After looking at these and many other sites our opinion is that LinkedIn is the place to be for professionals in general, but you should do your homework to see if there are more specific sites that could be of greater benefit to you in your particular field.