I keep the used ones in the original packaging, but write used on it with a sharpie.

When full, I take to my pharmacy where Sharps are disposed of. I know they are not potentially contaminated like medical sharps, but I think it is safer for all involved.

I use a washed-out plastic Parmesan cheese shaker. The one side has a half-hole, which is great to drop large rotary blades into, and the other side has little holes for regular pins. That side usually stays open, lol. I'm forever dropping bent pins into it!

I have one of the containers they use at the doctor's office for needles. I put all bent/broken needles and pins plus the rotary blades. When it gets full I take it to my doctor's office and dump it in with theirs. They think it's hilarious that I have a container like theirs!

I have a sturdy plastic container that mints originally came in. It's nowhere near full, even after 3-4 years. When it does eventually fill up, I'll probably tape it securely so that it can't pop open, and throw it in with the regular trash. The only person who manually handles our trash is DH, who puts it all in a trash can and rolls it down to the road. The can is specially shaped so that a big mechanical arm on the trash truck reaches out, picks it up, dumps the trash into the truck, then sits the empty can back down in our yard. (Pretty cool to watch, actually! :D ) The truck hauls it straight to the landfill. They have heavy equipment to deal with the trash, so it's very unlikely that anybody but DH ever physically touches it. :)

I love the parmesan cheese container idea! :thumbup:

I put old blades from fabric cutting in a yellow container for cutting paper then when they won't cut paper I put in a small plastic container and tape up securely and put in trash. It takes a long time to get to the trash time after 8 years quilting just trashed my container.

I reused the yellow container that the blades originally came in and mark OLD on the outside with a Sharpie. When full, into the trash. I keep the skinny envelope that Crystal light or Starbucks Refreshers come in to put my discarded needles and pins in and toss them in the trash.

I put mine in a plastic container that held chewing gum. Holds the blade nicely and I open the flap to drop in the used sewing machine needles. Do not know what I will do when it is full! I must not change blades as often as I should because it has been with my machine for at least 3 years!

I drop them in an empty pill bottle.

I have the sharpener that OnebyOne talked about. Take it to my weekly quilt group so everyone can sharpen their blades. Works very well,

I use a sharpie and mark them as used, then I use them to cut my cardboard, It makes quick work of it, and with a bad shoulder I have trouble tearing it into pieces. This way I can cut it up and stack it.
As far as tossing them, just use one of your old containers. There's no need to dispose of them like sharps at a doctors office! They aren't contaminated with body fluids or disease! Just put them in something and toss them.