Your cover letter is a very important tool you can use to market yourself and interest a potential employer. Here are a few resources to help you write an effective cover letter:

Online Resources:

Ferguson's Career  Guidance Center  - The library subscribes to this  database of career information that you can access online using your library card. Once you are logged into Ferguson's, choose "Skills" from the menu at the top and look for the Cover Letters section. You will find advice and sample cover letters here.

Websites:

The Riley Guide: Cover Letters & Other Correspondence

About.com: Cover Letters

Books:  

Cover letters are a very important piece in your job search.  They are often a potential employer's first impression of you and  a chance for you to market yourself  so it is vital that your cover letter is well-written. These books and websites  provide sample cover letters and tips for writing them:

Books

15 Minute Cover Letter by Michael Farr and Louise Kursmark  

202 Great Cover Letters by Michael Betrus

Cover Letters for Dummies by Joyce Lain Kennedy

Gallery of Best Cover Letters by David F. Noble

How to Write Better Resumes and Cover Letters by Pat Criscito

Downloadables

101 Best Cover Letters by Jay Block and Michael Betrus

Websites

About.com: Cover Letter Samples

Monster.com: Resumes & Letters

Quintessential Careers: Cover Letter Tutorial and Cover Letter Samples

The Riley Guide: Cover Letters & Other Correspondence