Sell scrap metal
Check the garage or that heap in the backyard for old swing set parts, metal toys, and other bits of metal that you can scrap for cash.
While it may not garner you a huge lump sum, scrap metal is definitely a good resource for quick cash.
Iron, steel, aluminum, brass, and copper are the most commonly traded types, and you can also check around for prices, too, if you have some more time on your hands.