I'm so sorry to hear about your father-in-law and of the situation that has been thrust upon you and your family. As you've found out, sometimes when we try to shield our loved ones from pain, we actually do the opposite.
While I would also point you to the same thread as Marty, I'd like to add a couple of other ideas for you. You might consider getting a nice journal for your spouse and letting her know that it should be used as a grief journal. I've found journaling to be a very powerful tool when working through grief. It is a private action that allows one to spill all of those emotions, all of that garbage one is feeling, onto the page - as well as serving as a tool to help clarify those feelings. It has been a great tool for me when I've gone through loss of my own. For the doers of the family, you may wish to start organizing final arrangements (ie: gathering necessary paperwork for selling property, finding insurance paperwork, locating bank accounts, thinking about or making funeral arrangements, etc.) While these are things you may or may not want to discuss with your father-in-law, they may help you feel like you are doing something "productive" as well as giving you control over part of the situation.
One quick and easy read that I would recommend is "Tuesday's With Morrie." It deals with one man's struggle with the impending death of his mentor. It is a very entertaining read that has a lot to say about anticipatory grief, but be cautioned that it is not a step-by-step self-help book. It is truly a story. However, it may speak to your situation. You may wish to read it yourself, or give it as a gift to one of your family members.
I hope that this helps. Again, I am sorry to hear about your father-in-law. I will keep your family in my thoughts.
-Greg