Manuals for your machines, sewing, serging, or what have you.

Most good machine companies have your manual online as a free download nowadays.
So, If you are looking for the basics on your machine, whatever machine that is, the company's website is an awesome place to start.
So, here are a few to get you started...

Singer
http://www.singerco.com/accessories/manuals.html
You need your model number.
If you can't figure it out, Singer has a little chart to show you where you might find it.
http://www.singerco.com/support/model_number.html

Brother
http://www.brother-usa.com/manuals/default.aspx?ProductGroupID=3&WT.cg_n=Support&WT.cg_s=Manuals

Kenmore
Not so easy with the info, but they have this nice page to help you along...
http://homeappliance.manualsonline.com/manuals/mfg/kenmore/kenmore_sewing_machine_product_list.html

Janome
Choose your machine, click Specifications, in the upper right corner there will be a link to download your manual.
http://www.janome.com/index.cfm/Machines

Juki
http://www.juki.com/downloads.html

White
Like Kenmore, they don't make it easy.
http://www.whitesewing.com/customer.asp

Bernina
http://www.berninausa.com/news-n486-sUS.html

Pfaff
Currently they are charging, but they have a notice that "coming soon" the manuals will be available for free download.
I'm not holding my breath.
http://www.pfaffmachines.co.uk/pfaff_instruction_books.htm

Husqvarna Viking
Not so helpful, but here is the contact list...
http://www.husqvarnaviking.com/global/406.htm

There are many, many other machines out there.
You will find neighbors, relatives, friends, and even strangers who have one in a closet that they want to give you.

Use your google fu to find the manual if it didn't come with one.
Try typing the machine's maker and the word manual i.e.; "singer manuals" or "singer 9444 manual" or "Toyota sewing machine manual" or use the phrase "instruction booklet".

When the person gives you the machine (or sells it to you) ask if they have a box or bag of notions or fabric or stuff that came with the machine that you can have too. Chances are, that manual (and extra feet, bobbins, needles and other treasures) will be inside.
Give them your contact info in case they find the manual later. You'll be surprised at what people will send you (like a cigar box full of vintage buttons from the 1930s they found in grandma's closet). They just want stuff to go to someone who will use it.

If all else fails, send me an email and I'll try to find it for you.