Ladies and gentlemen, SlimBean...
Official SlimBean Changelog
Google Code Port Page
NOTE: The rom does not contain Gapps. Gapps can be found on the SlimBean addons page (see below).
Clean install or coming from another ROM:
Download the zip
Addons (if you don't have it already) from here. Make sure you download addons for android 4.1.2 NOT 4.2!
Full wipe, and manual format /system
Flash the zip AND the addons you want, reboot
Download the zip (Rom also has OTA Updates)
Wipe cache and dalvik-cache
Flash the zip, reboot
No need to flash the addons again
Need more space? Use Link2SD!
Official SlimBean Sources
P500 Port Sources
Kernel courtesy of LGICS
OTA Updater courtesy of OTA Update Center
Screenshots from P500 in second post.