Just a further note on Bernina feet. They use their own system, not like anyone elses and in their infinite "wisdom" they changed mounting type. So if you've got a classic Bernina 830, it takes "old" feet, I think the numbering is black, but the "new" 830 should use the "new" feet which I think are red numbered. They do make an adaptor foot which will allow you to use generic feet...but I bought my Nina used and it came with a real Nina walking foot. I'm not sure about using an adaptor with a generic walking foot.
You can find both Singer or Simanco feet and a company named Griest or Greist (I've seen it both ways) also made add on feet.
Singers generally come with a standard stright stitch foot (and/or a zig zag foot if the model does that stitch) plus a ruffler, an edger, a small hemmer, a wide angle hemmer, a multi slotted binder, a button foot, a shirring foot and a tucker. You can also buy a darning foot, a 1/4 inch foot of various types, a walking foot, or almost any modern foot to fit your shank. You can also buy an adaptor if you have screw in feet to convert your shank to use flat press on feet.
They also had available a buttonholer of different vintages, going from all metal to plastic "jetson" oval boxes with some plastic and templates inside. They should also have a feed dog cover with the BH.
They made an add on zig-zagger with some templates and then sold boxes of others. I know there are red and blue and I think yellow and green.(i'm not at home to check right this min).
They made a picot edger that could sew two delicate edges together without overlapping.
There are probably more that I can't think of now, but I've had great luck finding the green cardboard boxes of attachments at thrift stores and yard sales. I don't know why, but they seem to get separated from the sewing machine itself. You can also get almost any foot on ebay or from the vintage shops on line...or a lot of them from a modern bricks and mortar store.
If you're interested in some of the feet that I've picked up you can take a look here:
http://www.quiltingboard.com/t-116176-1.htm
I've given this reference before, but I know it's a pain to look back for it.