For you, Silver-Midnight, I highly recommend Writing the Short Story: A Hands-On Writing Program, by Jack Bickham, one of Jim Butcher's mentors.
amergina recommended Donald Maass' Writing the Breakout Novel. Jess Haines suggested The Fire in Fiction, also by Maass. Others have suggested the use of a beta reader, or posting in the SYW area (whose gates are closed to me, and, considering the infrequency of my posting, are likely to remain shut for some time).
Does anyone have other resources they'd recommend? Whether it's particular exercises, books, blogs, and so on.
Others may approach it differently, but to me, learning-by-doing seems like a serious waste of one's time and energies; why reinvent the wheel when you can reverse-engineer it? Why figure out the techniques of top chefs through trial and error when you can take classes, read articles, or watch video instruction? I don't mean to insult those who learn differently, I'm merely trying to express why I personally would prefer to hear advice rather than reassemble tidbits and smidgens from my reading and experimentation.