Mute my phone, when I'm at work, university, theatre, cinema or wherever. That's one of the things AutoMute can do for you. It analyzes the WiFi networks in your surrounding area, matches them to rules you specify and applies the settings you define.
Select WiFis by their names (SSID) and AutoMute applies settings if they are in range.
You can set ringtone volume, whether to vibrate or not and priorities. The geeks of you also can use regular expressions for SSIDs.