The process I describe as "deriving scope from goals" in the book is very good to manage scope creep. I've used techniques described there to control the scope of large enterprise projects and web gaming platforms alike. the key idea is that you limit the number of business goals a single milestone can achieve (I shoot for one goal at a time, but you might choose differently), and then work towards recognising stakeholders and values that the system needs to provide to achieve that goal. Google for feature injection and effect mapping to see some nice techniques to do that. See my whitepaper about effect maps. If you are based in London or near, you can come and hear me speak about that in about a week, and then some of my clients presenting an experience report. (see the event page on skills matter web site - they will probably film it so if you are not local you will be able to see a video there in about 10 days.
On more traditional projects, the same effect can be achieved with Goal-feature-requirement breakdown that Scott Berkun described in The Art of Project Management (he used it to control scope creep on MS Excel)