I love Google, Bing and Yahoo just as much as the next Internet user, but sometimes you really want to dig down into a particular subject.

In order to do that, you really need access to those underground search engines that may not be quite as well known, but they dig much more deeply into specialized areas of the Internet than the general search engines are capable of.

In many cases, these search engines are tapped into what is currently termed the “invisible web,” which is the information available on the Internet that standard search engines don’t have access to, because they are buried behind query forms or directory requests.

The following 6 underground search engines that I chose are not porn sites, illegal piracy sites or anything else that could get you in trouble with the law, or with your significant other. Instead, I term the following as “underground search engines” for two reasons. First, because they are so specialized that, although they are extremely useful, these search engines remain hidden from the general Internet population.

Second, because they provide a search service to a select community of Internet users who are interested in the specific subject matter that the search engine covers. So, in this article I’ll be covering seven “topical” search engines that I consider that best in that topic area.

#1 – The Best Torrent Search Engine

If you are a Torrent enthusiast, and you find yourself pouring through the hundreds of search engines that are available online for shared torrent files, then search no longer. Torrent Finder is one of the most impressive meta-search engines for Torrent files around. It methodically searches through over 170 torrent sites to identify the results that pertain to what you’re looking for.

The available list of Torrent sites that are plugged into this meta-search is impressive, and even more impressive are the search results. Now, I did say that I would stick to underground search engines that are not illegal, and many Torrent searches are done for the purpose of downloading copyrighted software, but the truth is that there are thousands of legitimate and legal Torrent files available. Torrent Finder is clearly the king when it comes to accumulating and presenting an aggregate of search results.

Here is a search for “classical music,” with over 300 results. Some keywords searches turn up a thousand results or more. The nice thing about the results from Torrent Finder is that you get a view of positive and negative comments, so you can get a hint that a file may not be legitimate before you attempt a download.

#2 – Free Bargains and Deals

At MakeUseOf, you’ll find a lot of excellent resources for how to find awesome deals, such as coverage of the great bargain search engine FreshBargains. FreshBargains aggregates results from 15 top websites, which is excellent. However, another fantastic and barely known website to find freebies is called Prospector.

Prospector is based in the Czech Republic, but the list of free stuff that you can find here knows no borders. We’re talking stuff for the home, free computer software, free educational supplies and tons more. In all fairness, the site is more of a directory of content, but with over 3300 categorized and reviewed links to freebies – it’s a body of information that deserves greater recognition.

#3 – House Sales and Sales Foreclosures

Earlier, I wrote an article about the best websites to find foreclosed homes. Public government sources seemed to provide the most information without requiring a paid membership. However, somehow I missed AOL Foreclosures. This foreclosure search engine sifts through various sources of foreclosure listings from all across the country (U.S. only), and unlike the paid sites – it offers price, address, and as much information about the property as is available. AOL Foreclosures is one of the unsung heros of free foreclosure search engines.

An even better as-yet unknown search engine that also deserves mention is Trulia. Trulia is yet another young search engine that provides collected real estate information from various sources, and offers it to you, the homebuyer, completely free of charge. No longer is it only for those who are “rights” to the information. With Trulia, you can see the current asking price, the address (most paid sites will leave that out for free members), square footage, and even whether the price was recently reduced or increased, and by how much.

Most importantly, the site also shows recent sale prices – which is information previously very difficult for buyers to obtain without a realtor. When you’re searching for a house, knowledge is power, and the knowledge that the Trulia real estate sales search engine offers will give you that power.

#4 – Public Records Search Engines

Another very common sought-after search engine that isn’t always very easy to find are those that offer free public records information. Nine times out of ten, if you try to find such a search engine, you’ll end up with results from one of the major commercial companies trying to sell paid public records search results to you. However, the Public Record Center is different.

While it is more of an underground “portal” than a search engine, it is actually a portal to some of the most obscure, yet useful, public information search engines on the Internet. Starting at this one site, you can find the government search engines where you can search for court judgments and liens, conduct asset searches, and even look up copyright and trademark information. With so much demand on the web for free access to public records – this is the perfect centralized location where you can access virtually everything.

#5 -  A Legal Search Engine

Ever hear of a search engine that lets you dig up legal information from the web? Neither did I, until I discovered Cornell’s Legal Information Institute. This amazing little search engine digs through the Institutes extensive legal library and pulls out any information that you might need. This could include family law, criminal law, labor law and much more.

For those of you who feel that you have what it takes to defend yourself in court, there’s also a very useful search engine where you can extract opinions from the U.S. Circuit Courts of Appeal.

There are similar search engines buried throughout this excellent legal resource. If you have any interest in law at all, take some time to check this one out – it’s a diamond in the rough.

#6 Paranormal Search Engine

Of course, if we want to go really underground, we’ve got to go paranormal. And there’s really no better underground paranormal search engine out there than UFO Seek. Don’t let the name fool you, this particular niche search engine isn’t just focused on UFOs and aliens.

UFOSeek covers just about anything out there that’s paranormal, as well as new age, alternative health, science, the occult, ghosts and just about anything else that you might consider “fringe.” It’s one of my favorite search engines on the net.

Now that I’ve gone over a few of my favorite hardly-known, niche search engines, offer some of your own! What are your favorite underground search engines that you wish more people knew about? Share your insight in the comments section below.