Jeffrey Thalhammer, who last wrote for The Working Geek on "On breadth vs. depth of technical knowledge", has strong opinions about resumes and cover letters:
Last week, my wife attended a "resume bootcamp" seminar. Among other things, I asked her what the seminar recommended for cover letters. According to the speakers at this seminar, the resume is far more important the cover letter, and they de-emphasized letter-writing skills. I was shocked!
In my experience with hiring, I'm far more impressed by a compelling and concise cover letter than a long and esteemed resume. To me, a resume is like a PowerPoint presentation and I don't mean that in a good way. It is usually a dust-dry list of bullets and broken sentences that lack any texture or color. Reading a resume is never fun or even interesting.
On the other hand, the cover letter is an opportunity to tell me a story that holds my attention and helps me understand you. As an expository document, rather than a declarative one, your cover letter can leverage all the literary devices of your language: cadence, phrasing, metaphors, symbolism, vocabulary, etc. These are what make your cover letter interesting, and make me want to talk to you.
A good cover letter indicates your ability to communicate with others, and in the software industry, it also indicates your ability to write code. If you can't express yourself elegantly in your natural language, then you probably can't express yourself elegantly in code either. I realize this judgment is harder to make with those who don't natively speak your language, but fundamentally, I believe it is still true.
This doesn't mean that you should write a five-page cover letter for each job -- economy of words is still important. Consider writing your cover letter as if you wanted to thrill the reader with a summary of the exotic vacation you took last month. Tell them what you did, why you did it, how it affected you, and why the reader should be interested in your story. Make it exciting and fascinating to read. Show me your energy, your style, and your personality. And of course, be professional too.
In their defense, the speakers at the resume bootcamp were all HR recruiters. Often times, recruiters are given only a list of keywords and skills associated with a job, and instructed to harvest as many compatible resumes as possible. From that perspective, I can understand why they would put so much more emphasis on the resume. But once the resume gets to a hiring manager, I think the cover letter becomes a much sharper image of the candidate. So in the end, you really need to have the total package: a great cover letter and resume. But don't neglect one for the other.
A note for hiring managers: If your HR department does not pass along the candidates' cover letters, you're not getting the whole picture on your job candidates. Ask your recruiters to pass along the cover letters and all the correspondence associated with any resume they submit to you. You can learn a lot by looking at how a candidate interacts with recruiters in the early stages of the hiring process.
Jeff Thalhammer has been specializing in Perl software development for over 10 years. He is the senior engineer and chief janitor at Imaginative Software Systems, a small software consultancy based in San Francisco. Jeff is also the creator of Perl-Critic, the leading static analysis tool for Perl.