Cast Iron Cookware- Many times you see rusty, beat up cast iron wares for sale for a few dollars each. They can easily be refurbished! After refurbishing, either use them yourself, or turn around and sell them online for a hefty profit! Here is how I renew cast iron: LINK
Enamelware or Stainless Steel Cookware- Especially stock pots! Stainless stock pots can run up into the hundreds of dollars. Large Enamelware pots double as hot bath canners. Toss those old toxic non-stick pans and start your stainless collection for pennies on the dollar.
Mason Jars- As witnessed on Pinterest, there are a million and one uses for mason jars besides just preserving the harvest- decoration, storage, candle holders... Snatch up any you see for sale less than $7/dozen! Be sure there are no cracks or chips in the jars.
Pressure Canners- Another big ticket item. I would avoid old school canners and pick up dial gauge canners with locking lids only. If you have a large garden, having a few canners in different sizes can save quite a bit of time. You can purchase replacement parts for modern Presto and All American canners.
Dehydrators- You can never have too many dehydrators when it comes time to harvest herbs, or when it comes to jerky making! Pick up any you find that have some sort of temperature control. (Ask to plug it in and make sure it works before purchase...)
Small Appliances- Especially Crock Pots, which you can also use for crafting (soapmaking etc). If you are lucky enough to find a Kitchen Aid mixer in good working order for under $100, SNAG IT! (Again, plug them and test them.)
FOR THE HOME
Oil/Kerosene Lamps and Lanterns- For power outages and decoration purposes. Aladdin brand lamps are extremely expensive new, however replacement parts are easy to come by online. If you come across an Aladdin, I recommend you pick it up.
Blankets, Sheets and Towels- Another "can't have enough of" items. I imagine some people are a little grossed out by the idea, but nothing a good washing can't take care of. Old towels come in handy out in the garage and barn. Sheets can be cut up and made into other items, too.
Furniture- Pinterest has a lot of examples as to what can be done to give new life to old furniture. Consider refurbishing and old piece for pennies on the dollar, rather than purchasing new. Older furniture was built to last (as I type this sitting on my 1930's couch).
FOR YOURSELF AND FAMILY
Books- Especially old "from scratch" cookbooks and DIY/how-to books. If you home school, you may also come across some college textbooks that would be great for home schooled high schoolers.
Board Games- Often seen in unplayed condition. Now days, most kids spend their time on XBox and computers, rather than play old school board games. Hosting a "Game Night" is a lot of fun, and virtually FREE!
Craft and Art Supplies- Especially yarn, fabric and thread, which can be made into clothing and other useful items.
Clothing- Obviously. Plain t-shirts, sweatshirts and jeans can be modified and embellished!
Tools- You can never have enough tools! Always seems the one we need at the time comes up missing LOL Plug and test power tools.
Ladders- Ladders are very pricey. Multiple ladders in varied heights come in handy when it comes time to paint the barn and hang holiday decor, that's for sure!
5 Gallon Buckets- Another item that can be used for multiple purposes- water for the animals, planters in the garden, tool storage, long term food storage.
Lawn Furniture- You can never have enough tables and chairs, especially if you're hosting bonfires and picnics! Chair cushions run around $25 each new, look for those, too!
Lawn Games- Again, if you host bonfires and picnics, it's always nice to have activities available. Keep the kids and their friends outdoors and busy all summer long!
So there's my short list LOL What would you add, and why? Have you ever made an exceptionally spectacular find at a yard sale?