I'm interested in Power Supply Unit design, currently. That can be done using a digital controler and a built-in analog converter module. All in all it covers a broad range of topics in electronics, because so many varieties of solutions achieve similar goals. It's my intro to advanced electronics and a focus on efficiency adds economics to the mix. Component selection, acquisition and testing seems to be an involved process and it's really interesting. On the far end, component design (e.g. coil winding) and tool building (say sensor setup).

For a start in electronics I know of MITx with prof. Agarwal, but it's based on his well priced book. There's a load of free texts on the basic elements and circuits. The Art of Electronics is often recommended and it seems rather comprehensive, but I have not read it yet myself - you might find it in a library. I recently read a neat report on a microcontroler based switch mode power supply. Before I found several analog chip manafucturer's application notes quite interesting and advanced. Power Supply design is pretty fundamental, too, as every application needs one. The difference between ideal current and voltage sources was one of the first things to learn for me.

The point being, to address the parent post, that high power design can be a completely different beast to mixed signal (stress on signal).