The "All-in-One Yard Sale Kit" is something I think should have been around before now. All you need for your yard sale in one shrinkwrapped rectangle. Someone sent it to me and I just got a chance to open it up and check it out:
The kit features one really big yellow sign (above), four yard sale signs (upper right, in a stack), 10 slotted tags with plastic loops, 20 item price signs, 5 sheets of price stickers, 2 sheets of double-sided tape strips, 50 small sticky hang tags, and 10 large white adhesive hang tags.
I've been to many sales with poor signage. These signs are just the right size and super colorful. Also, you could potentially reuse them if you use erasable markers. They're sturdy enough that they won't bend in the wind or fold over.
I think this kit is an idea whose time has come. My one suggestion for the makers -- and I'll have to check with them to see if this is not already the case -- is to make the signs waterproof...because often enough you find that it rains between the time the signs are posted and the sale itself. Or between the sale and when you get to taking the signs down.
But overall I think this is a convenient product that will be well worth it for anyone giving a yard or garage sale.