Kollwitzstrasse Street Market
I can't think of a better way to spend a Saturday then consuming a steaming bowl of Erbsensuppe (yellow pea soup) with a giant sausage submerged in it while perusing the almost too picturesque vendors at the Kollwitzstrasse Market. The market takes place every Wednesday and Saturday and I suggest getting to the soup-from-a-strange-truck stand early to beat out the crowds.
We like this market because we can get kale here. I realize that my street cred is destroyed by stating that, but it's true. I love me some salty, crispy kale chips. I also just love sunshine through the trees and crisp autumn days. So here's to that.
In Kollwitzplatz Park next to the market you can sometimes see the bubble man. He's cool. If I was a kid I would probably worship him.
Other suggestions nearby: try the wonderful new/used English book shop Saint George's and have a somewhat snooty coffee at Cafe CK on Marienburger Strasse. Saturdays can only be a success with such a combination.