I put a little introductory message in front of my email explaining who I am (my age, where I live, etc.) as well as where I found the ad and any additional information. I thank them for their time, etc. Just sending the resume, although informational, could just be confusing, and most people do not appreciate having resumes shoved in their face. Sending a nice little "hello, I am..." just seems more professional.
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So when you're happy (Hurray!), or sad (Aw!),
Or frightened (Eeek!), or mad (Rats!)
An interjection starts a sentence right.