I’ve been interested in the LPC1114 Arm M0 from NXP as it’s a 28pin DIP so it’s easy to use on a breadboard but it’s also an ARM M0 with a nice (free) development environment and only costs ~ $4.00. The LPC1114 also allows very cheap hardware design as it only needs 2 resistors and cap for a fully running system (no crystal !).
http://chiselapp.com/user/jschimpf/repository/LPCLights/index is a link to a site about the hardware and software to run NEOPIXEL strips with this processor. The hardware design has the level shifters to convert from the 3.3 V LPC1114 to the 5V of the strip. Also level shifters are there to handle the SPI type strips. The site has an Eagle CAD based board design for the system.