I recently discovered Opbeat. It seems to be a simple (and free/cheap) alternative to Newrelic, at least if you're using Django.

Opbeat supports release tracking (like Newrelic does, too). That means that your deployment setup can log all deployments together with the git revision number via the Opbeat API. That helps you to identify issues that occur when deploying a buggy version (or performance improvements when deploying optimizations).