Evri is a search engine that offers a service that has great potential for helping learners conduct research.

What Evri does, besides serving as a search engine, is show users the topics that are connected to their search term. For example when if you search for information about Adolf Hitler,  Evri provides results on one side of the page while on the other side of the page showing you a web of names and topics related to Adolf Hitler. See the screen shot below to see how Evri displays connections.

Try it out and/or take a closer look at http://www.evri.com/.