I'm a UI/UX designer interested in writing about design. I've written about the principles of iOS design, a case study on how I designed an iPhone app, etc., in my blog (http://radesign.in/blog/).
Instead of writing what I think is useful I want to write what the audience finds useful. So, what about UI/UX design you wish you knew? What would help you? What do you find interesting? What would you like to know?
I learned to program typing in code from books and magazines, and, later, from reading and rewriting parts of open source projects that did things similar to things I wanted to do.
There's lots of ways to learn development like that today, online, including great open source books like Dive Into Python and Think Python and Learn Python the Hard Way.
There isn't so much of that for design. Not online, anyway.
I don't write about "how to design" because, like programming, it's something you have to learn by doing. There's no Learn UX the Hard Way, but maybe there should be.
One of the projects I tried once was running design workshops, so I could tease out repeatable design exercise and publish those: http://vi.to/workshop/premise.html I ran fifteen workshops, and ultimately discovered they were structured great for the attendees, but wrong for my goals.
There's a book, The Non-Designer's Design Book, which is pretty proscriptive, but does give you exercises you can try and repeat. There are other books, like Editing By Design, which tell you "why" certain things are important, but doesn't include exercises.
Critique is a related problem: most interactive designers today didn't go to school for it, so they're missing the common cultural and academic background that fine artists, architects and industrial designers have, where they've learned the history of the practice, learned fundamentals, and practiced constructive criticism for years.
I don't know if you're any good as a writer or a designer, but if you're looking to write about design and make an impact on non-designers, you could do worse than to take a design pattern or an element of design and make exercises around it. Give people ways to practice them, to study an implementation, to apply it something new, and to critique it, repeatably.