If you are the lucky owner of a GSM version of the Samsung Galaxy Nexus device, you will be pleased to know that Google has begun rolling out the Android 4.2 version of Jelly Bean to your device. Of course, the rollout will go out in groups, so if you haven't received yours don't fret, it will be coming within the next few days. This new version is Android 4.2 Jelly Bean (build JOP40C). If you want to check manually to see if your device is ready, just head to Settings > About Phone > System Updates on your phone.
If you are a savvy dev or tinkerer, then you can update your device manually. Of course, you will need to be on build number JZ054K and also have a custom recovery on your "Takju version of the phone" if you want to flash the software.
Here's a download link: Android 4.2 Jelly Bean (build JOP40C).