I've already done several posts on this subject, but darn it if more good material keeps getting posted. I love the internet. (The link above is for the first post of a series on plot.)
Straight from QueryTracker: 9 Steps for Plotting Fiction. Good, straight-forward stuff.
And, for those of you who love to use flashbacks, but aren't sure when/how to use them: 3 Tips from Writer's Digest
This last link isn't ONLY plot and structure, but it's good. Here are Things Every Reader Wants from a Writer