1. Computing

Underground Search Engines

Search engines you can use to dig into Invisible Web content

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Underground search engines are search engines designed to dig deep into the hidden, or invisible, part of the Web not easily accessed by general search queries.

The following underground search engines focus on a wide variety of content areas - books, medial information, images, torrents, etc. You can use these search engines to unearth hidden gems of content.

1. Mathematics and Science

Whether you need to solve a complicated math problem or look up scholarly discussions of eclipses, the following search engines can help you find solutions to a wide variety of mathematical and science-related questions.
  • Ten Things You Can Do with Wolfram Alpha: These Wolfram Alpha shortcuts will help you frame your queries more efficiently and retrieve hyper-appropriate results.
  • Scirus: Scirus is a science search engine dedicated to only searching science-specific content, including journals, peer-approved articles, and academic research.
  • Medical Search Engines: Use these medical search engines to find answers to your medical questions, get more information about various health topics, or just to learn about something new.

2. Books and Printed Materials

Whether you're looking for a rare book, a used book, an audio book, or a comic book, chances are you can find it on the Web using one of these excellent book search engines that focus purely on books, magazines, and other printed materials.

3. Social Networking Sites

Search within popular social networking sites, or search across a wide span of different social sites; you can do that with the following search tools.
  • Twitter Search Engines: Here are the top five best Twitter search engines that you can use to find people, popular content, links, and much more.
  • Six Ways You Can Use the Real-Time Web: What is the real-time Web? Basically, the real-time Web is simply a catchphrase for almost instant information, from conversations to news to collaboration. These search engines help you target exactly what you're trying to find on the real-time Web.
  • Social Mention: Social Mention is a a search engine that focuses on social Web errata to find information on social networking sites.

4. File Hosting Sites

There are literally millions of files uploaded every day somewhere on the Web.

5. Torrent Files

Torrent search engines make it easy for searchers to locate files across a number of different bittorrent sites.
  • The Top Torrent File Search Engines: If you want to cut right to the chase and start using the best torrent file search engines on the Web, you're in the right spot. In this short but sweet image gallery, we're going to look at the top five torrent file search engines on the Web today.
  • The Top Torrent Sites: There are so many torrent sites on the Web! How do you know which ones are the best? Here are the top ten torrent sites where you can consistently find good quality torrents to download.
  • The Top 20 Torrent Search Engines: Here are the top 20 torrent search engines as vetted by usability, relevancy, and access.

6. Images and Multimedia

Whether you're looking for an image, an obscure video, or simply want to see the latest and greatest movie trailers, the Web is a good place to look. Here are the top underground search engines that take multimedia content and focus on making it as searchable as possible.

7. The Invisible Web

The Deep, or Invisible, Web holds much more content then what you can find with a general search engine query. The following search engines can help you access that material.
  • How to Mine the Invisible Web: The Ultimate Guide: The Invisible Web is a mammoth resource that is mostly untapped. Learn how to discover Invisible Web resources with this comprehensive, ultimate guide to searching the Invisible Web's goldmine of information.

8. People and Family Search

Finding people, communicating with people, keeping in touch with people....these activities are the most popular on the Web, and with good reason. Connect with others you might have lost touch with with underground people search engines.
  • Invisible Web People Search: The Invisible Web is a goldmine of information, and since the Invisible Web is larger by far than the parts of the Web we can access with a simple search engine query, there's potentially much more information available.
  • Use the Web to Conduct a Background Check: Want to get information on someone you know, or see what's on the record for yourself? You can use the Web to do a free background check via a multitude of free sources.

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