Android Open Kang Project, or better yet known as AOKP, has just released their Preview Build of Jelly Bean for both the GSM Galaxy Nexus (MAGURO) as well as the Verizon Galaxy Nexus (TORO). The ROM runs on the latest version of Jelly Bean available, Android 4.1.1.
As noted, this is only a Preview Build, so the AOKP team has only just started adding in their well-known customizations, status bar mods, etc. You can bet that there will be more to come as time moves on, as the AOKP team never fails to impress.
If you’re interested in trying out the ROM, you can find the download links in the Google+ source page, and download the ROM for your respective device. Note however, that if you run into any troubles, we aren’t responsible.