My 3 yard sale finds in 3 years of yardsaling. I've probably gone to about 100 sales but sometimes you find some gems.
The first was two years ago when I found a kid selling his original Clone Turbo Tank in box for $15 and a Tie Defender for $5. I offered $17 and he took it. The Tank had most of the figures missing as well as the speeder bike, so I ended up selling it on Amazon for a nice profit.
The second one was 40 pounds of Lego for $50. The family had a bunch of toys out so I asked if they had any Lego. One of the boys said he had some at his house. I was surprised when he came back with 5 bins full of Lego and only wanted $50 for it all. After sorting through it, I found the original Hagrid's Hut, HP Forbidden Corridor, HP Final Challenge, original Republic Attack Gunship, original Millenium Falcon, Imperial Shuttle, a bunch of the mini SW sets, five or so old Ninja sets, the old Shuttle Launch Pad, a couple of Divers sets, and a bunch of other stuff. They all have varying degrees of completeness, but I obviously couldn't complain for the price. I had to sell off the rest of what I couldn't sort (about 24 pounds) because we were having a baby and we needed the room.
The third was the original Hogwarts Castle for $5. The lady was still putting stuff out, so I asked if she had any Lego. She said she'd be right back and came back with a small box with a half built Hogwarts. I saw some of the minifigs were there and it looked mostly complete so I asked how much. When she said $5, I quickly took out my wallet gave her a five and raced out of there

It's missing the manual, but I put it together and it's about 95-97% complete :D