The following is a slightly edited version of something written by Jeff Williamson:

About Goals and Objectives - One common problem was coming up with specific things you want the site to accomplish, and not just saying "the site will provide information." I think that most of you probably have a sense that "provide information" is not a very effective or measurable goal. So what is a good goal or objective? Something you want the web site to accomplish - a problem you want solved (lack of information is rarely a problem), or some standard you want reached, or some behavior or impression you want the web site to create in the user.  I'm not very picky about this, as long as it's more specific than "provide information."  Here are some possibilities.  The site will... 

+ increase membership
+ facilitate contacts among members
+ encourage contacts among members
+ facilitate officer elections (e.g. voting could be done through the web site)
+ make printed materials available on the web for wider distribution at a lower cost
+ be friendly to search engines
+ be searchable by keywords and phrases
+ be accessible through a wide variety of hardware/software setups
+ encourage the user to ask further questions
+ direct users to their nearest office of whatever
+ make the site printer-friendly
+ inform registered users via e-mail of news
+ encourage frequent use of the site (through things like latest news on the front page)
+ provide easy contact with and enrollment in professional organizations
+ facilitate contacts between the director and employees
+ accept and encourage employment applications
+ enable users to plan and book their trip from the site with links to existing travel, hotel, and outfitter services
+ enable users to contribute information to the site
+ enable users to give feedback on the site
+ allow users to read each others' feedback
+ give the users clear, rich images of the lovely places represented by the site
+ enable users to purchase additional information from the site (and earn me $$ as an Amazon associate) with links to online book and media retailers + be informative? Educational? Interesting? No, you can't be - or it's really, really hard to be - all three at the same time
+ showcase student work
+ make it easier for users to register for the program
+ promote the program
+ work with other promotional materials for the program (e.g. the URL will be printed on brochures)
+ encourage contact with the department for more information
+ provide additional resources for use in the program
+ provide online versions of frequently used papers in the program

Keep in mind that you're making a web site instead of doing something else with your time and problems to be solved. If your site is about sea slugs, you need to consider why people need to learn about sea slugs, but also why they need a *web site* about sea slugs. Again, I'm not picky about the answers here, and I'm not thinking about anything complex - I just want you to address "why a web site about this" 

Well, one more last thing - the adjunct to "why a web site about this" is "why ANOTHER web site about this?" In other words, if your site is going to provide news, information, and sports with a focus on Washington D.C., you have to, at some point, consider why on earth anyone would read your stuff instead of the Washington Post online. Try to position yourself in the online world. Often your position is unique just for representing a unique entity, such as a class, business, or institution or sea slug farm.