In my mind i have this solution:
1) Crete something to store list emails, which subscribed to blogs or news (in can be dynamic module, form, or something else)
2) Subscribe to IDataEvent and then send notification to all this emails
Make Sitefinity work best for you.
Progress, Telerik, Sitefinity and certain product names used herein are trademarks or registered trademarks of Progress Software Corporation and/or one of its subsidiaries or affiliates in the U.S. and/or other countries.