Nuuu Slimroms has been out since Android 4.3 and was one of the first to release for Android 4.4 kitkat thus changing Slimroms to SlimKat. Slimroms releases weekly beta for 4.4 current Slim rom is weekly 1.9 beta. According to the Slimroms site we their latest weekly 1.9 is that start of their new theming engine. They brought back the real dark Slim to 4.4 which btw is now Android 4.4.2 for the latest Slim weeklys. My favorite part of SlimKat is that they were one of the first releases of kitkat for Grouper the Nexus 7 and had weeklys. On the first release they already had interface options and slimIRC. With SlimKat weekly 1.9 beta Android 4.4.2, features range from interface settings with clock and battery options. Navigation which allows you to change navigation bars dpi. SlimKat also features Slim OTA and SlimSizer which allows you to receive over the air updates and remove any built in APP. But BE careful with what you remove.
Sources : http://www.slimroms.net
For developers: http://www.slimroms.net