fmtjatt
Here is a link to lots of free cover letter samples. I have used these in the past..

Orthodox_Ted
Keep it short and to the point. Highlight achievements relative to the position. Always say that I will call back in a certain time period to discuss qualifications.

sassy_91
NEVER use colored paper. Use resume paper, in ivory. Put a page border around the letter, but not an overbearing one, just something simple. Things like that get it noticed. First paragraph - What job are you applying for and where did you hear about it. Second / Third paragraphs - you education and what qualifies you for the job, hard skills and soft skills, courses taken Last paragraph - "My resume is enclosed; references, transcripts and letters of recommendation are available upon request. A personal interview can also be arranged at your convenience. Thank you for your time and attention. I hope to hear from you soon."

misslabeled
It's all about "white space" for both your resume and your cover letter. Graphics, borders, fancy fonts, and all of that turn off hiring managers. They are too busy looking and so being "eye popping" is not a good thing. It's the substance that should make it attractive by being clear, concise, well-formatted, and by all means SPELL CHECK, and not just with the computer program. Read it yourself on a hard copy. That said, a cover letter should be simple. Start with what position you're submitting your resume for and where you found out about the opening. Avoid tired phrases and cliches like "Enclosed please find..." Just get straight to the point, "I am submitting my resume in response to your advertisement in the Los Angeles Times seeking a receptionist." Read the job posting and address each of the qualifications they ask for, "I have worked in the manufacturing industry as a receptionist for three years and am familiar with both Microsoft Word and Excel. I have also operated multi-line switchboards and maintained petty cash accounts." Stop trying so hard! It's really not that hard. :) Good luck!

bigbadboss.com
If what you mean is you want the hiring manager's eyes to pop when he or she reads your letter, then research the company and include a statement in your letter that indicates you are aware of its current focus on something specific. Then explain how your skills can help in that area. Make it more about the company than about you--your resume is all about you--they want to know what's in it for them to hire you. Here's a link to some examples: Good luck!

globalreach
some free sample resumes and cover letters are available in my profile, check them out, all the best :)