First things first: skip the cheapie salt and pepper mills at the store. They are built to be one-time use, and are not refillable. And believe me, I've tried to refill them. My last empty pepper grinder had to be thrown away because I couldn't even open it to recycle. I have since bought nice, grown-up, refillable salt and pepper mills.
Whether your spice jars are empty because you use fancy magnetic or matching jars, you used all the spice, or that paprika was seven years old, there are many things you can do with the empty jars. I tend to reuse the glass jars more than plastic ones, although both can be reused. Want to decorate them before reusing? Scrub off those labels and get crafty, my friends.
- Tiny vases for herbs in your kitchen or wildflowers (or greenery) at your desk
- Essential oil reed diffusers (use glass jars for this)
- Containers to bring to the bulk section of your grocery store (especially if your store sells spices in bulk)
- Travel containers for jewelry or beauty products (the plastic ones could work well in your 3-1-1 carry-on bag)
- Pet treat jars
- Travel vitamin containers
- Thumb tack or paper clip jars
- Craft containers (especially for jewelry making)
- Bobby pin or hair tie jars (how cute would a row of mismatched spice jars look in your bathroom??)
As a side note, most herbs and spices have "best by" dates compared to expiration dates, so they last longer than you may think! Herbs and spices beyond the date are still good, but not nearly as flavorful as fresher ones. In general, ground spices last between three and four years, leafy herbs last one to three years and whole spices can last for four years.
Eat By Date has a very comprehensive chart of how long many specific herbs and spices will last. It may help you save money by not throwing out jars that can still be good!
Check out a Treehugger list of seven ways to use spices that may be too bland for cooking but that are still useful. Bonus Eco Cajun eighth way - Easter egg dyeing!