I just used the coffee grinder method, after putting the candy canes in the freezer for 20 minutes. The result...truly magical! After only a few seconds, the candy canes were completely powdered!

I actually just wack them with a rolling pin while they are still wrapped then cut the end off the wrapper and pour them in the bowl. Works great!

Two heay-duty bags are better than one. Hadn't thought of freezing first. One thought: Look for loose peppermints, unwrapping the little b*****s is a pain!
VoE

place them in a ziploc freezer bag and smash them to bits with a rolling pin or mallet. very therapudic for holiday stress.

Put them in a zip-lock bag with most of the air squeezed out, and beat hell out of them with a mallet. Relieves lots of frustrations.

Freeze and smash in mortar with pestle.

I have a mallet with a resin-like plastic head used for hammering Ikea-type furniture together without denting or destroying it. I have crushed all kinds of things using this tool, including nuts. I think peppermint would work well. I put the item in at least two heavy duty ziploc plastic bags and pound away. You can see your work and adjust accordingly. It's fast, simple, and there's no mess.

I've actually frozen them first before smashing with a pan or meat pounder-- the freezing helped to make them more brittle.

I usually put them in a freezer bag first and then wack them to bits with the meat pounder.

I'm laughing because I made a flourless chocolate cake for a party tonight and I wanted also to dust it with crushed peppermint. But I made the mistake of buying soft round peppermints instead of candy canes. They were too big to fit into the chute of my coffee grinder, and I broke my mini chopper trying to chop them in that. So I ended up slamming them with a meat pounder. It worked, but I've been vacuuming up peppermint bits all day. :)

I break them into about inch long pieces by hand and then whir them in a coffeegrinder. You can control the coarseness, and it works like a charm!