I’m curious about designing some websites and applications for personal (and potentially public via open sourcing) use. I’m an experienced programmer, but I have mostly worked with backends, programming language implementations and lower down the stack.

My question is how do you learn to design any application? I’m not asking about the frameworks or toolkits involved, I am sure I can figure that part out myself. My focus is on learning about the aesthetics and user experience of an application and the process involved in creating that. How do you go about acquiring this skill? What are the first (preferably open/free) resources you would point at?

To start with, I would like to design a theme for my blog, then maybe functionally “rice” my desktop environment and emacs configuration. Finally, I might create (or contribute to) some FOSS applications to solve a personal problem.