This submini USB scope is based on a Atmel Tiny45 cpu and cost less than 5€ with a homemade pcb.
It has 2 analog inputs and can supply 5V ont the 4 pins header on the right. One of the inputs can be scaled down with the trim pot.
The firmware in the Tiny45 is written in C and compiled with Winavr and usb source code from obdev. As you can see, there is no crystal , the software sync the internal 16.5Mhz pll clock with the USB clock.