Love this question--love yard sales! I'm always scouting around for craft supplies, but I love finding some unexpected treasure, too.
Before I had my complete collection (1981-2011--yay!), my favorite thing to do on a Saturday morning was to seek out old volumes of Christmas With Southern Living. Every time I would find a volume I didn't have, I would jump up and down and whoop it up. I know they thought I was crazy, but I didn't care!