This extension refreshes block cache after saving the product. Used to fix "One or more of the Cache Types are invalidated: Blocks HTML output." message.
Extension is tested only on Magento ver. 1.7.0.2
Keep in mind that this extension is created for purposes of blog article at inchoo.net and as such can only be used as proof of concept. If you find it helpful in order to learn Magento, that is great, but be careful if you plan to use it in production environment.