Cover Letter Websites

http://jobstar.org/tools/resume/cletters.php

This website explains that a good cover letter should be free of grammatical errors, directed to the person who is interested in hiring you, and writtten in natural language.  Meaning, it should sound authentic and not generic.  Always do your research about the company you want to work for so that you're in the loop and can surprise the employer with information. 

http://www.phdjobs.com/how-to-write-a-brilliant-cover-letter/

Remember that the interviewer or recruiter will have a pile of CVs to get through, so make your comments are relevant to the vacancy, and ensure that they go straight to the point. Where possible, highlight key information to make it stand out, or use bullet points to draw attention to the most important messages. Always use ‘selling’ words, and remember that you have just 10 – 20 seconds to grab the attention of the reader.

http://www.askamanager.org/2007/06/what-does-good-cover-letter-look-like_13.html

Really good cover letters show personal interest in working for a particular organization, and it’s specific about why, which makes it both more believable and more compelling. It’s human nature — people respond when they feel a personal interest from you. Works in dating, works in job-hunting.