Probably the most commonly used search tool is Yahoo!, which classifies the most commonly consulted Web sites by subject. (It can also be searched by keyword.) Its major disadvantage is that it is selective in its choice of pages -- only a small fraction of WWW pages are indexed, although the maintainers have tried to ensure that they have chosen the most useful and commonly accessed pages. Excite is a similar, but much less accurate, directory.
Several WWW indices attempt to collect information about many more pages. In my opinion, the most ambitious and most successful of these is Digital Equipment Corporation's Alta Vista index, which covers more than sixteen million WWW pages. Other indices that I have found useful include HotBot, Open Text, the Infoseek Guide, and Lycos.
There are also more specialized search tools for finding information about individuals and businesses. Switchboard and Four 1 1 are national telephone directories. People Search can also be used to obtain telephone numbers and addresses, and includes a reverse-lookup facility (given a telephone number, it tells you who the number belongs to). Road Map makes available a street map for any location in the United States.