Postmatic is a great option for both your WordPress commenting system and post notifications.
Gravity Flow allows WordPress administrators to automate custom, form-based processes such as approval and feedback/review loops via Gravity Forms. Watch my walk-through of this dynamic plugin.
The Event Calendar WD plugin for WordPress is feature-filled with the options to control multiple calendars on a single WordPress install.
Learn how the GF Chart extension takes your data collected from Gravity Forms and creates easy to read charts for a great visual overview of the data.
The Forge plugin is a front-end page builder for WordPress and offers tons of options to help you build a dynamic WordPress site without knowing code.