I just had a research project where I needed to find past employees of a certain company. I thought this would be somewhat tricky, but ended up being an easy task. Here is some useful info:

• LinkedIn: LinkedIn gets a big round of applause in this research area. I have used the service in the past to house my connections and my personal info, but today this service became invaluable. I found so many great leads simply through searching for the company I was after. From there, it was completely easy to do other searches to back into contact information.
• Today (March 31) I just realized that the name of the contact can only be seen if they are in my personal network (meaning that through the linking of my connections there is a link to the person at the company). I didn’t realize this in my initial search. I have noticed that finding names for companies in the technology space seems to be easy as my network consists of technology people. However, finding someone in perhaps the retail space is a lot trickier. I did notice that when researching the tech space a plethora of names resulted from the search; whereas very few within the retail sector. This means that 1) obviously more tech people are interested in the LinkedIn service and 2) the more my network grows, the better of a research tool this will become 3) as a research I would like all information just to pull up, but from a personal viewpoint I am glad that my info could only be seen if I was located within a network
• VentureSource: VentureSource is great if and only if the company is private and has been financed. If the company has gone through an exit, VentureSource stops tracking it, resulting in the useful info only being in the private realm. VentureSource is very extensive on the research and provides the board members of the private companies. If the contact being searched for is affiliated with a private company, this could be a good first stop.
• Wink: Wink is a VC funded people search engine. I thought it would be very similar to ZoomInfo and never provide me with any useful results. My first search pulled up results that were anything but I was looking for. However, after re-defining my search I received applicable information. What I instantly liked about the service is it is a search engine/aggregator of information already on the net, and it references where the info is located while providing the direct link.
• In reference to my LinkedIn comments above, Wink helps you find people outside of your network. This option might be available to premium users of LinkedIn, but alas I am not one of them.
• ZoomInfo: Zoominfo is known to be a search engine for contacts, but to be honest I have never had it prove useful. I don’t know if this is because I don’t have a premium subscription, but to be honest, I have had zero luck without a premium subscription so why would I ever invest? That being said, I still use it to see if it can find any info I have missed elsewhere, but have yet to be successful.