My current main project is building a Tesla Coil. Mainly because I find them fascinating, but also to get some experience in high power electronics. The idea is to make a Continuous Wave Solid State Tesla Coil with support for PWM modulation for audio playback. Audio streaming and configuration/tweaking of the controller is supposed to happen wirelessly via WIFI. This far I have created the primary and secondary coils, a high-current full bridge inverter plus an ATxmega256A3 based controller with WIFI support. And written a huge amount of firmware and other software to support it.