We all know what's new in Jelly Bean, and you'll get that with CyanogenMod 10 -- plus a more customisable launcher, some extra tweaks on the lock screen, themes, and a few extra apps.
Stable releases started showing up yesterday for a small number of devices, but we're seeing more and more added to the list, including the Samsung Galaxy Note, Samsung Galaxy S III, HTC One S, Galaxy Nexus, HTC Evo 4G LTE, Nexus 7, and many more. Click here to see if your device is suppored. If it isn't, click "All" in the left sidebar of that page -- you might find an experimental build you can try for your phone.
CyanogenMod 10.0 Release [CyanogenMod Blog]