This System tray alternative mod let you to hide notification when you are working, just right-click on it and press hide notification. This simple mod it's a pure hack, it's missing some feature..like no sound when notification are off.
Extract the archive
enter in the build dir
sudo make install
Add from plasma widget selector system tray alternative.
Thanks to gnumdk for providing the first modded version: http://kde-look.org/content/show.php/System+Tray+Alternative?content=119268
Works on KDE > 4.4