What do I put in the "Current or Most Recent Courses" of the Common app if I don't know my classes for next semester?
They ask for all my classes for the whole academic year, but our schedules for the spring aren't released till winter break
First, write out all your classes for this semester and figure out which classes are full-year classes like Math, English, History, or Science and carry them over to the Spring semester. Then if you have any graduation requirement like Art or Health or PE you haven't taken yet, add those as well. The only thing you will be missing are a couple of electives so take your best guess what electives you might take for the Spring semester.
That should be as good as you can enter for the time being.
This fall before you submit your application, you can talk to your counselor or make tweaks as required on the common app.
Best of luck