The wait has been a long one, but it's finally starting to come to a close. The CM team has officially released several RC-level builds of CyanogenMod 9 for many high-profile devices, including the Galaxy Nexus (GSM), several Galaxy S II variants, and the Nexus S and Nexus S 4G.
For the complete list, head to the source link below. As always, make absolutely sure that you're downloading the correct ROM for your device, and if you have any reservations, ask in a forum before flashing, and always make a backup first. Otherwise, happy flashing!
Update: The folks over at the CyanogenMod blog have just officially announced what we already knew was available, and the total number of devices with an available RC1 is 37, so head over to the downloads page to see if you're on the list.