There were no errors at all in the cassandra server logs, so I figured it must be something with Python, since cqlsh was running inside of Python.
Any time I would run a command (other than help) in cqlsh, I would get a "Segmentation fault: 11", with this in the details:
Process: Python  Path: /Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python Identifier: Python Version: 2.7.3 (2.7.3) <snip> Crashed Thread: 0 Dispatch queue: com.apple.main-thread Exception Type: EXC_BAD_ACCESS (SIGSEGV) Exception Codes: KERN_INVALID_ADDRESS at 0x0000000000000000
This turned out to be a bug in Python < 2.7.6. An upgrade to Python 2.7.6 solved the issue.
A note on Python's site referred to
Python 2.7.6 was released on November 10, 2013. This is a 2.7 series bugfix release. Most importantly, it resolves an issue that caused the interactive prompt to crash on OS X 10.9. It also includes numerous bugfixes over 2.7.5.