Sometimes, I need an alert mute on my phone or desktop, usually both, and only temporary. I get email alerts on my phone all the time, and also on my desktop. They are interruptions, and I want them to just go away for a while and let me think. That's not an option when everything uses its own process for sending notifications to the user. I installed a Chrome plugin called Chime to unify my alerts for Gmail and Facebook, but that, coupled with Outlook using its own alert system, plus SMS and another Gmail notification system on my phone still made for a lot of interruptions coming my way on some days.
I tried Growl for Windows, which seemed fairly good, but to get Gmail and Facebook notifications with it, I needed to run two more apps in my system tray. Oh, and I had to code a special macro to get Outlook alerts. It did allow some greater control, but it wasn't what I was looking for.
Mokalus of Borg
PS - The best option, I think, is to just keep alerts to a minimum to begin with.
PPS - If I need them off altogether, I'll just set a timer to remind me to turn them back on later.