If you contacting a company without responding to a job posting or without being contacted by them, be sure to state clearly why you're inquiring - just stating that you need a job and you love their product is not going to be enough. Try something like this:

Hi - I looked through your posted jobs and while you currently don't have any open positions that meet my qualifications, I'm a huge fan of how your company combines the functionality of a lawn mower with the safety of an overstuffed couch. I'm wondering if my background as both a small engine mechanic and furniture upholsterer might be a good fit for your company. I've attached my resume to this email and if you'd like to learn more about me and my professional background, please do not hesitate to call or email me.

Sincerely,

Lon Moore
[phone]
[email]

See how the note is specific about what Lon might bring and why he might be a good fit?
By attaching both a resume and including his contact info, Lon increases the chances of being contacted by that company at some point in the future (or, perhaps, immediately).