A cool tool to get things of a similar kind from a few given samples. I think its a great tools for targeted online research, which will fill you with absolutely relevant stuff in first attempt, which is a bit harder to do with search engines.
For example click the following link, which was given soap, rpc and dcom as samples, will yield an interesting result on related technologies.
try this one: (sql server, oracle, mysql)
and even this: (aspx, asp, jsp, php)
and try it yourself at http://labs.google.com/sets