This video and the related links are very useful in understanding inclusive component design and in general creating simple and usable web designs.
Below are some resources referenced in the above video:
Inclusive Components blog/book.
BBC GEL (Global Experience Language) reference.
Form Design Patterns book.
A related blog of interest from the above author is Every Layout. This provides a fresh perspective on layouts and modern CSS. It makes you appreciate the stuff you get for free from modern HTML and CSS and also helps you think about how to create flexible layouts without relying so much on media queries.