I offer my big, bright room in the heart of Kreuzburg/Neukolln. It's 2 mins away from 2 main metro lines (U7 & U8 at Hermanplatz) and surrounded by grocery stores, bars, cafes and restaurants.
It's great for connections to both airports and the train station.
My room has its own projector, so plug in your laptop and feel like you are in a cinema!
You'll also get the hang with my lovely 2 housemates in the kitchen, which also has lots of light.
Check-in and check-out if flexible.
Very easy to get to from both of Berlin's airports - minimal walking and transport changes, so no problems with luggage.
Just put the address in (SENSITIVE CONTENTS HIDDEN) and you'll be fine.