A site named SiteVolume with the help of a nifty little tool can give details of different kinds of vocabulary words that are used in popular social sites like MySpace, Digg, and Flickr. SiteVolume gives the result in the format of a bar graph to show the occurrence of a particular word or a set of words appearing on each of the popular social sites. If you are confused for the kind of keywords you should use for starting your search, then you can simply compare the frequency of those keywords on these sites and use the most popular one.
It is quite interesting to compare the name of Web tools, search engines, and technologies on this site. The overall presentation of the site is sleek, but the methodology it uses to get details of the numbers is quite simple. It is simply like a Google search. If you want to know more about their methodology, you can take help of the questions and comments page of the site.