I have been reading a fascinating new book entitled, The CIO's Guide to Breakthrough Project Portfolio Performance: Applying the Best of Critical Chain, Agile and Lean by Mike Hannan, Woldfram Mueller and Hilbert Robinson and I highly recommend it if you are in a multi-project environment. I have worked with Mike and Hilbert and I assure you they are both class acts and are very experienced with project management tools and techniques.
This book presents nine techniques from six distinct origins, spanning the Theory of Constraints, Critical Chain, Agile, Lean and a couple of innovative "add-on" approaches developed by the authors. No technique is overly complicated, and all are proven, yet this book is the first to bring them together harmoniously into a single, integrated PPM framework designed to pick the highest-impact projects, and to deliver as many of them as possible, as reliably as possible.
I would encourage everyone to check this book out, especially if your business is in a project management environment. It's a quick read, but full of very valuable methods to make your project come in on scope, on time and on budget.