What’s the point of smartphone camera if you can’t take clandestine photos with it? The stock Galaxy Nexus camera app can’t (easily) be silenced, but you can get around that using Camera360.
After installing the app, select a mode and then open the settings menu by clicking the gear at the bottom right in portrait orientation/top right in landscape. Under “Common Set,” clear the “Shutter Sound” checkbox. Exit the settings and you’ll have silent picture taking.
Of course, there are many other things Camera360’s good at, but IMO the UI is so confusing those features are nearly unusable. The fact that it’s free and easily solves a major issue with the Nexus’ native Camera app makes it a good download though.