Don't just let your server crash on an unhandled error, finish everything you were doing first. Multiple techniques used to ensure your clients don't get socket hang-ups. Cluster support and graceful shutdown on SIGTERM too!
Make sure you know when your Node.js process crashes: output the error to stderr, append it to a file (synchronously), increment a statsd counter, send it via email, and send it via SMS. Cover all your bases in case of loss of filesystem access or internet connectivity!