Things that you won't have to buy from GDRNT since the garage sale is a virtual on-line garage sale:

Legwarmers
Parachute Pants
Broken furniture that you swear you'll fix and use, but you never will so it'll sit in your garage forever until you donate it back to GDRNT to sell over again
Acid washed jeans
Boys clothes sizes newborn-3T ---hey actually if anyone is looking for these i have a bunch to sell, some hardly ever (actually a few never) worn---
Another exersaucer for your almost-toddler since its such a good deal and benefitting a charity
Used dog bed that your dog is just going to pee on since it smells like another dog
200 plastic bins for crap in your garage--oh--i think dennis actually uses those---

Need I say more? Much better option just to donate in lieu of buying garage sale stuff anyway!