What's a good way to notify a user they have a message

What's a good way to notify a user they have a message

  
I'm working on an app that has a notification component. When something happens in the app, an email gets generated to whoever should get it. I would also like, if the user were logged in, instead of sending the email, notify them in the app and let them see the message right there.

What are some ways you think would be a good way to let the user know they have one or more messages and allow them to open them up and see them? Also, do you have any examples?
Hi,

Try IconBadge from Silk Framework.