My women's Bible Study just began a new focus on the Psalms. Our goal is to apply what we learned about redemptive history / biblical theology from the book God's Big Picture to a few specific Psalms.
But we don't have a book that we're working from, so I did a little bit of searching through a variety of resources and came up with the following summary framework for us to look at the Psalms. It's a little rough, but I thought there might be a few people out there who would find it interesting...
FYI - my main resources were Transformed by Praise, by Mark Futato; Prayer and the Knowledge of God: What the Whole Bible Teaches, by Graeme Goldsworthy; The New Dictionary of Biblical Theology; and An Introduction to the Old Testament by Dillard and Longman.
[Let me know if you have trouble reading it and want a "full size" version.]