List of free feature stuff for developerππ½
If you're looking for all programming tools around feature (not just free). Check this page List of feature Programming Tools

Unleash
Feature management lets you turn new features on/off in production with no need for redeployment. A software development best practice for releasing and validating new features.
Tag: feature, deployment, testing
Hosted by you Canary release (Gradual rollout) On/Off Targeted release Experimentation (A/B testing) Kill switches Community support