This is a basic implementation of an rpm (revolutions per minute) meter of an encoded wheel using an AVR ATtiny2313 microcontroller. The motor used is a solarbotics GM8 purchased from Pololu.com for $6 USD.
The display is a parallel character LCD which uses the popular HD44780 chipset, which I found incredibly easy to drive. I started out driving this display using pushbuttons, and after two commands I was outputting to the screen. The attached C file shows the simplicity (in my opinion) of the program. You can get the avriomacros.h header file here.
I built this in preparation for using the quadrature encoders on the 12V motors from pololu as the next robot I'll be working on is a self-balancing, two-wheeled bot.