There is no email subscription by default. There are events to which you can subscribe (ContentManager.Executed) - whenever a blog post is created/modified. Then, you could send your emails. For blogs, however, you can subscribe via RSS, which is working out of the box.
There are again RSS (out of the box) and ForumManager.Executing/Executed events.
In both cases the current item that is being created can be taken from the event command arguments (e).
the Telerik team