I just started using Answers.com and am pretty happy with it so far. It works with Wikipedia and other sources to find the answers that you need and if a term such as "VoIP Peering," isn't in it's database, it does a search for you and you can click on the various results to get the answer you are looking for.
The interface is seamless. In your web browser you just hold the Alt key and click on a word for a definition to come up. In communications where new acronyms are coined by the hour, this is a great resource. I almost forgot to mention -- when you click on a term, your results return in a new browser window.
The program can also install on a desktop, there is also a toolbar that stays at the bottom of your screen. I didn’t find these options useful as I can just save www.answers.com in my favorite's folder if I need access to its services.
The company generates revenue via Google ads.
In other dictionary news, my VoIP dictionary is now in it's second edition and now has over 10,000 terms. If you are looking for a desktop reference, you won't want to pass up on the opportunity to order it at www.voipdictionary.com.
TMC also has an exclusive agreement with www.techtionary.com. This site gives tutorials on many of today's most important technologies. These are real video/flash based tutorials that can give you volumes of information in a few minutes. If you are interested in sponsoring terms on this dictionary or licensing this dictionary for use as an internal or external resource, please contact Dave Rodriguez at firstname.lastname@example.org.