I just found two new wonderful resources - one for theory and one for practice.
Design Philosophy Papers is one of the few online journals (as opposed to blogs, let's say) that focuses on theoretical questions motivating design. As the editors write,
Design Philosophy Papers (DPP) comes from a longstanding desire to gain greater recognition for the study of design by the intellectual community at large, as well as our frustration with the market-driven conservatism of design publishing. It aims to break away from the idea of design as a specialist interest, as well as rejecting the simplistic and debased way design arrives before the public via both old and new media — frequently merely as style or technics.