Persistent notifications in Unity
Solution 1:
I read an article about this quite a while ago, so I don't know if it's working at this moment. The package is called "Recent Notifications" and can be found at: https://launchpad.net/~jconti/+archive/recent-notifications
The original article where I read about it:
http://www.omgubuntu.co.uk/2012/03/how-to-never-miss-an-ubuntu-notification-again
How to install via the terminal:
sudo add-apt-repository ppa:jconti/recent-notifications
sudo apt-get update
sudo apt-get install indicator-notifications
Remember to log out and log back in.