This was originally intended to be a short, simple project to generate a sine wave using a 1 MHZ crystal oscillator. However, it turned out to be a lot more complex than I thought, and took quite a lot of tinkering before I got anything even close to a sine wave. It's still not perfect, but it does produce what appears to be a sine-wave output.

It is a simple circuit, but choosing the resistor and capacitor values was the critical part to making the crystal oscillate. Even with the correct values, I didn't get a clean oscillation, as can be seen from the oscilloscope picture.

On the breadboard in the first picture is a frequency generator module I bought from Ebay, a very useful tool that I was using for testing purposes.