If you do freelance work, then you send out your resume on a regular basis. The cover letter to your resume is critical because it represents the first impression of your work.

Freelance Writing Jobs has a Cover Letter Clinic series with tips and information for writing the perfect cover letter. Here is a tidbit from that series:

"I’m not sure if I would start a cover letter stating you’re the perfect candidate. If this is your first line, you have a lot to live up to with the rest of your letter. So if your first words are how you’re perfect, you’d better darn well prove it. I also don’t believe it necessary to say how you’re a native English speaker, if your letter and samples are well written, your skills are apparent."

Freelance Writing Jobs also posts available freelance jobs daily. It is a great source for finding work if you are a freelancer.