I have a few that I sometimes use. Since you mentioned it, I don't remember seeing any stencils at the last show I attended.

I don't know if the OP was referring to hand, fmq or long arm stencils. I'm a hand quilter so tend to focus there. Also, haven't been to a show in a while..last one was Lancaster a couple of years ago. I'm also close enough to Lancaster to pick up so great stencils there. But I will also say, one of the best places for HQ stencils that I've ever run across was at a LQS in ABQ in NM. Just wish I could remember the name of the shop. I picked up several for my stash. Many of which I've never seen before. They were awesome.

I've thought about using a stencil on a border but I'm afraid I will screw up my quilt. Is this procedure difficult and does the paint make the fabric stiff?
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As long as there are still quilters who quilt on their DSM, there will always be stencils. I collect most of my stencil stash in the 90s. This company is still in business:
http://quiltingstencils.com/

Betty62: if you want to use painting stencils to stencil a permanent design on cloth, check out dharma trading co. Online for setacolor or jacquard fabric paints.
But the others were discussing stencils to stitch the quilting.

I am a hand quilter so I do love stencils. I find them at my LQS and Joanns. We have a lot at my quilting group ,too.

I also like to use my stencils for hand embroidery.

They always have them at my quilt shows. I purchase them online. I know the ultimate stencil is pretty popular

Back in the day Walmart use to carry a large assortment of quilting stencils. I bought one of each when the old Walmart went out and moved the the Super Walmart. Most are very big to fit one square, Sunbonnet Sue stencil, scenes with tree and bunnies, butterflies, cables, feathers, cross hatch, stipple, border corners, etc.

I thought one day I'll have time to hand quilt and I'll need these. LOL. I think I paid .25 for each. They are on the pink stencil sheets, very sturdy. When something is dirt cheap compared to the retail price I buy. Now I don't have to pay $ for a stencil.

I did the same as Onebyone - bought a lot of stencils years ago, haven't used them yet. But I do plan to try in the near future.