From their site:
The purpose of Alltop is to help you answer the question, “What’s happening?” in “all the topics” that interest you. You may wonder how Alltop is different from a search engine. A search engine is good to answer a question like, “How many people live in China?” However, it has a much harder time answering the question, “What’s happening in China?” That’s the kind of question that we answer.
You may notice the Alltop.com widgets on this blog and even the badge I now display. You can now find this blog, The Art of Education, as well as many other great sources on Alltop.com's Education page.
If you are looking for a good place for searching topic specific information, give Alltop.com a look.