Hey mate yeh I was thinkin about this myself the other day. I was told that if you dont have a cover letter you have to make sure your resume is saying all the important things that a letter would say eg relevant skills etc. This is very effective if applying for multiple positions; keeping in mind that this is what employees care about most, not what you got in the hsc or how many school awards you won. If you do decide to do a letter though, make sure you know the relevant person's (eg manager, recruiting officer) name as saying "to whom it may concern" or whatever sounds like you havent researched the business your applying for, which will come across as you not caring enough.