Although I love my two, lightly-computerized Berninas, I learned to sew on older mechanicals. My mom had a Singer 500, a.k.a the Rocketeer. And the sewing machines we had in my junior high home-ec class were old Singers very much like the one Susan is writing about. (Her descriptions of needles, threading, and tension on her 15-91 triggered a lot of forgotten memories!)
I own three vintage sewing machines right now. The first is a Singer 401A. I bought it on e-Bay because it looked so much like my mom's 501. It has cams for making special stitches and I managed to find a box of attachments. I also have a buttonholer for this machine, though I have to admit that I haven't tried using it yet. It comes in a pink plastic box shaped like a football.
I also have two Featherweights:* one which I inherited from my mother-in-law, and one which I discovered at a yardsale. I've got a box of attachments for both of them, including a buttonholer. I haven't yet tried out the buttonholers for any of these machines, but Susan has just posted a detailed (and well illustrated) tutorial that will finally will finally give me the courage to attempt it. Even if you don't own one of these, check it out. It's fascinating!
*Um, not a picture of one of my own machines, just a link to show you what a Featherweight looks like.