It's a great day to be an Android geek -- the Ice Cream Sandwich source code is now being pushed to Google's git servers! This is the full release of Android 4.0.1, which is the version that will ship on the Samsung Galaxy Nexus. Most readers won't need to do anything here except wait for their favorite developer to get things rolling (hi, Beezy!), but those who are technically inclined and feel like cooking up a bit of their own ICS can find new build instructions here at Android's source project pages.
Two things worth noting here -- the code is huge, and it's going to take a couple hours to transfer over. If you try to sync now, you'll get something that is never going to build. As Jean-Baptiste Queru points out, it's best to wait for word from Google that it's finished pushing out. Also, as-is the code will only build for the Galaxy Nexus, and it's going to take some tinkering to get it to build for other phones. Builds for other products will be coming from Google shortly. We're excited, and as soon as the code is done pushing, we'll be at work to get a version built for the Nexus S.
Source: Android Building Google group