This one's going to be obvious to most people, but I have read a book that says to do the opposite, so:
A lot of the scrum / agile guys advise against splitting your schedule up by resource: don't have a bunch of "QA" tasks that are estimated separately from your "Designer" tasks that are estimated separately from your "Coder" tasks, and are all tracked independently, because that creates an us-against-them mindset. "We desinger types are done with our responsibilities, it's you coder types that are holding us back." It should be one-for-all, all-for-one: if you're falling behind, your designers and QA guys and whatnot should find ways to help in whatever way they can, even if it's just getting coffee for and giving back massages to those poor coders. *Agile Estimating And Planning* is one book that recommends this practice.