Did you know you can use the Course Search in Vergil to filter for classes that have open seats?
Select “Only show classes with open seats” in the search results!
There are a bunch of other useful things you can filter for, including classes that satisfy Barnard General Education (Foundations) requirements, classes with a particular number of credits, etc.
NOTE ON FOUNDATIONS REQS: for Barnard requirements, it's safest to cross reference anything found here with the Slate listing of courses approved for Foundations requirements.
NOTE ON LAB SCIENCE: Do NOT rely on Vergil for acceptable lecture-plus-lab science pairings. See recent blog post for more info on this.