LineageOS - Operating system for smartphones and tablet computers, based on the Android
Pixel Experience - PixelExperience is an AOSP based ROM, with Google apps included and all Pixel goodies (launcher, wallpapers, icons, fonts, bootanimation).
Evolution X - #KeepEvolving!
crDroid - crDroid is designed to improve the performance, reliability and customizability of stock Android.
ArrowOS - ArrowOS is an AOSP based project started with the aim of keeping things simple, clean and neat.
MIUI - Xiaomi MIUI Official Global Site. MIUI is a customized Android ROM developed by Xiaomi for smartphones and tablets. MIUI Forum offers ROM downloads for 251 devices including Mi 6, Mi MIX 2, Redmi Note 4 and others.