If you're a prolific ROM flasher and you've got a Galaxy Nexus or another recent Android device, odds are pretty good that you've at least tried Android Open Kang Project (AOKP), one of the fastest-growing family of custom ROMs out there. The project has released over 30 builds since its inception late last year, and is now on Milestone 5. This doesn't mean much beyond the fact that they've reached a point where enough new features have been added to justify upgrading for those who don't flash nightlies as a habit. You can see the release notes and downloads for dozens of devices here.
Android Open Kang Project already has a great selection of custom features integrated from various mods and open source Ice Cream Sandwich ROMs like CyanogenMod 9. Some of the notable additions include kernel upgrades for the Galaxy Nexus, various camera fixes and a whole lot of squashed bugs. You can now add single-square widgets and various settings like the LED flashlight to the navigation bar as well.
All of the AOKP devices haven't been updated just yet, but heavy hitters like the Galaxy Nexus, Galaxy Tab 10.1, Motorola XOOM, Asus Transformer TF101 and HTC Incredible all have Milestone 5 builds ready. If you've got a phone or tablet that isn't supported just yet, just wait a week or so and the nightly team should have it ready. Coming from an AOKP build later than 30 shouldn't require a full flash, but anyone trying AOKP out from another ROM will need to wipe their device first. Keep those Nandroid backups handy.