RC Servo hack
Took apart a few RC servos while building the robotic arm that measures magnetic field.
Turns out the Hitec uses an Atmega48 as a controller with a pair of 5A MOSFET drivers. The ISP pins (MOSI, MISO, RST, SCK) are broken out to exposed vias. That means I can reprogram it with my own control algorithm (PID tuning in mind), change the control interface (UART serial instead of PWM), or have it do different things entirely.
At $20 a piece it also makes a good platform for experimenting with feedback control and PID-related stuff.
The HS-7954SH also uses the same Atmega48, although with a slightly different driver circuit (it uses the ME4542).