InfoMin, RefSeek, and iSeek
KidsClick and SweetSearch
For science students and teachers, we recommend Scirus. They search 545 million sites that are specific to science to help you sort through the massive amount of information out there and target your results.
Need help with history? A site called Timelines allows you to search by the date or the event. This makes it super easy to learn all about a particular topic.
VisuWords is a great English resource for upper grades or advanced students. This online graphical dictionary helps you build your vocabulary by graphically linking words to their meanings and associations with other words and concepts.
Wordia is aimed at lower grades and gamifies vocabulary search and learning, making it the most fun search engine on our list.