Students increasingly turn to the Internet to help them with their coursework. Subject directories can be especially useful, whether you are in search of a movie review or a biography of Galileo. However, subject directories - like many online tools - can sometimes blur the distinction between information and advertisements.

Subject directories are collections of links to web sites, categorized into different subject areas. Human volunteers or employees can perform this task, or it might be automated by way of computer programs. Subject directories may be made by anyone, but there are two main types of directories.

Academic or professional subject directories are created and maintained by experts, for other experts. In contrast, commercial subject directories are geared towards the general public and are meant to generate revenue. Such directories make a profit by attracting as many visitors as possible so that they can sell advertising on their sites. Advertisements can be obvious or more subtle, ranging from a banner at the top of the page to paid listings within the subject directory itself.

Paid listings in commercial subject directories create an obvious problem. While it's understandable that the site's creators are in business and need to generate income somehow, the general public isn't aware of such practices. Thus, many people assume that the information contained in all subject directories is selected for quality and relevance.

On the contrary, commercial directories rarely screen link submissions for quality, and questionable links may be included if their owners are willing to pay for placement. Although the US Federal Trade Commission (FTC) has standards that subject directories must follow for disclosing paid listings, not all sites are up to snuff. You will find the same conflict with many search engines, which also sell advertising space in the form of paid listings.

Subject directories are most useful in the early stages of the research process, when you're trying to come up with a general topic idea, or if you need to narrow a broad idea down a bit. Using what Reva Basch (in Researching Online for Dummies, 1998) calls the drill-down approach, you can take a very broad subject heading and, step by step, break it down into smaller parts until you have a narrow, manageable topic to work with.

For example, let's say you need to write a paper for your American History class, but you're plum out of topic ideas. No problem! Using a subject directory, you could start with the broad subject of History. Under this heading is a list of countries; since you're taking an American history course, you'd choose the United States. Under the US, you might find a list of time periods to choose from; if you know which period you're most interested in, you'd make a beeline for that heading and explore the possible topics. If not, you might browse each time period until you find a topic that sounds intriguing. Using this approach, you're sure to find something to write about!

Subject directories can also be useful if you already have a topic in mind. Simply find your topic in the directory, either by clicking through the directory until you locate it or by conducting a search with a search engine (which many directories are equipped with). Once you have located your topic, you will have a short list of highly relevant resources to help guide your research.

It's best to use subject directories early on, when you're conducting preliminary research. If you have problems defining a topic, subject directories are most helpful. With directories, you don't have to formulate search queries, which require that you have a rather specific idea of what you're researching. Instead, you navigate around until you find an interesting topic, which the directory defines for you. Subject directories can also be helpful if you need to locate some high-quality, peer-reviewed resources rather quickly, without having to wade through all the results a search engine would give you. Your best bet is to look to subject directories if your topic is fairly current (but old enough that it's no longer breaking news), and has received a good deal of coverage. Obscure and out-of-date subjects are less likely to be included in directories.

When using subject directories for academic research, it's wise to rely primarily on academic or professional directories. Not only are they unlikely to contain paid listings (and, in the rare instances that they do, the paid listings are clearly labeled), but the links are carefully chosen by qualified experts in the field. As a result, you have a better chance of actually finding your subject covered in academic directories. You can also rest assured that any links included lead to reputable resources that are suitable for your needs.

If you do decide to look at commercial directories, try to find ones that disclose their listing policies and clearly label paid listings as such. By all means, critically evaluate all the information you find online, and apply more stringent standards to commercial directories, search engines, and web sites.