You DO need a cover letter for your resume.
The purpose of a cover letter is to introduce yourself and explain your intentions. By not sending a cover letter with your resume you are asking the recipient to guess what it is you want, something that most busy professionals do not have time for. Your cover letter does not have to be long-winded, simply tell the recipient what position you are looking to fill, why the recipient should consider you for the job (or even read your resume for that matter), why you are interested in considering a position in the company, and any particular skill set that would make you the best candidate for the job.
” Cover letters: types and samples | Career Services | Virginia Tech .” Career Services | Virginia Tech . N.p., n.d. Web. 17 Nov. 2011. http://www.career.vt.edu/jobsearchguide/coverlettersamples.html
“Purdue OWL: Cover Letters 1: Quick Tips .” Welcome to the Purdue University Online Writing Lab (OWL). N.p., n.d. Web. 17 Nov. 2011. http://owl.english.purdue.edu/owl/resource/549/01/