Is there a voice action shortcut in ICS? Android 4.0 doesn't have a magnifying glass search button like most pre-ICS phones.  I'm actually one of the people who used the long-press search button often with voice actions.  

Is there a similar shortcut in ICS, now that it doesn't have the search button, or am I stuck going back to the home screen/app list?
Are you using the Galaxy Nexus?  On your home screen you will see the "Google Search" bar.  On the right, inside this bar, you will see a microphone symbol.  Tap it.

I believe you are stuck going back to this screen.