How to enable silent mode during calendar events? I'd like to disable all notification sounds whenever there is a current event in Calendar. How can I do this automatically?
Llama will let you do this, and it is free (Tasker costs money). It has many of the features as Tasker and Locale, and it can even use Locale plugins. I have grown fond of this app and have set up many automated events.

To do this in Llama, you create two events and two profiles.

Profiles


Create a new profile and name it something like "No Notifications". Uncheck all of the volume options except for Change notification volume. Set the volume level to 0.
Create a second profile and name it "Normal". Again, uncheck all volume options except for Change notification volume. This time, set the volume level to whatever you want, like 5/7.


Events


Create a new event.
Under Actions, click Add Condition and select Calendar Event. Use the defaults.
Next, click Add Action. Select Profile and choose your silent profile.
Create a second event. This one will be the opposite of your first event, so change the condition of the calendar to "Event finished/Not current event" and set the action profile to your normal profile.


The developer of Llama is still working on it and adding new features, and you can get details here.