I always got told that resumes shouldn't be more than 2 pages, because generally speaking they are looking through a whole bunch at a time and you need to be succint and make an impression or they won't bother... when you start going for 'real' jobs after uni though you should make your resume as long as it needs to be without being stupid... ie only include the really important stuff and if that stuff happens to be 4 pages so be it..
as for cover letters, they can be as long as they need to be in order to address the selection criterea. Kepp in mind though the level of detail about yourself that is nessary to the position because if it is inappropriately long you won't get a look in. If you are applying for a retail position in a fashion outlet maybe don't go into so much detail. If you are applying for an administration role with formal selection criterea make it as long as it needs to be to get your point accross without being to wordy... I have written alot of cover letter for others the majority being over 4 or 5 pages (keep in mind these were for jobs over 40k a year, not $10p/h supermarket jobs). For senior roles it is common for cover letters to be 8 -10 pages.