The Galaxy Nexus is nearly as old as the Nook Tablet that CyanogenMod resurrected a couple of days ago with CM13, but it won't be getting that fresh of a software update. It'll have to do with a slightly older version of Android, but any third-party development on this forgotten Nexus is a welcome change from the state that Google left it in.
Officially, the Galaxy Nexus was abandoned at Android Jelly Bean 4.3. When KitKat was released in September 2013, two years into the Galaxy Nexus' lifespan, the phone wasn't deemed worthy of the new dessert flavor (allegedly due to the TI chip), but CyanogenMod's team of zealous and reckless developers braved the elements and kept supporting it with CM11 nightlies and snapshots. Now the team, which had been stalling at CM11 for over a year, has taken the Galaxy Nexus on a big leap to a new CM 12.1 nightly. That's Android 5.1 and it's at least 4 API levels higher than Google ever dared to go.
This being a first nightly, it won't probably be very stable for daily use, but it could still be fun to fire up on an old and nearly discarded Galaxy Nexus to mess around and try things. The download weighs about 248MB and you'll need this GApps package to get your Google flavor on the phone. Grab it from the source link below.