Anything useful on the Web involves database technology in some manner. Some examples include an 800 number directory, or a searchable database containing a list of job openings at an employment agency. Fourth, change your site often. Sites which change every one or two weeks may as well not even exist in terms of exciting visitors to return. People want to know that there's new and interesting stuff to peruse at your site.
Good sites change every day.
Fifth, leverage the overabundance of useful information. Take Yahoo for example. Yahoo is an extremely interesting searchable database that categorizes almost everything of interest known to the Internet community. No one has been able absorb all of the information that Yahoo has to offer in just one sitting. That's the strategy.