I love rummage sales. It helps to have particular things that you're looking for -- don't buy things impulsively. One thing that's always on my list is canning jars. I picked up about a dozen from Freecycle recently, but got a few more this weekend at a rummage sale for 25 cents each! Make sure to check that there are no cracks or chips so that they will seal properly.
I also picked up a fancy mini bundt pan (these cakes make great gifts or potluck items!), as well as a mandoline. While I love my food processor, sometimes I don't want to drag it out... or it can't do exactly what I'm looking for. I'm eager to try both out this week. We have some sweet potatoes that I'm going to try to turn into (baked) french fries. Yum!