How do you reuse trays that Cesar dog food comes in?

You can use them to organize crafts!

Yes, organize your tiny, itty bitty items. Sewing pins, straight pins, certain buttons, needles and the list goes on......then place them in a drawer, maybe marked if they have lids, or however. Good Deal!!

Spray paint them (if possible) seperate earrings, earring backs, rings ....etc :) Keep us posted :))

All of the above for sure. Great thinking folks! I would add office supplies like paperclips, binder clips, pens if they fit, etc. Hope that helps! Here are a few posts that are for recycled plastic, too.

http://www.hometalk.com/diy/organize/storage-ideas/reusing-lunch-meat-container-27550975

http://www.hometalk.com/diy/craft-room/craft-supply-storage/use-fuji-apple-containers-for-ornaments-and-yarn-23138966

http://www.hometalk.com/diy/craft-room/craft-supply-storage/reusing-tomato-containers-for-crochet-thread--18151094

What about using them as little trays for holding paint, glue, modpodge, etc? Or to hold screws and nuts while working on a project? Or how about as soap molds?

Jewelry. I organize mine by color because I Love inexpensive colorful jewelry, particularly in summer. I have too much, of course. But if I’m looking for reds, they’re all in one section. And the black pieces are neatly? all together. Orangish? Yup. Helps me finish my look of the day in no time at all. These look like they’d stack several in a clear plastic shoebox.

If you do any small paint crafts the containers may be good for mixing watercolors or acrylic paints.

And if you do any gardening perhaps punch a hole at the long end of each container and string a bunch of them together loosely. Hang them in the garden so the wind can blow them to scare birds etc.

I would use this for either sewing threads and needles or jewelry. Great for organizing small things.