I wrote down a whole page of thoughts and ideas while reading the book, but the one I'm really looking forward to trying is The Fiscal Fast. The idea is to go for a full week without spending any money. A few things that come to mind as potential challenges for us would be milk for our son and gas for my hubs. The latter actually shouldn't be too much of a problem because he could always use my car, which is only filled up about every two weeks, or he could carpool with a colleague.
The author talks about an annual hard-core fast, I'm thinking about a monthly/bi-monthly moderate fast. Basically, it means we make meals out of what we have in the pantry, frig or freezer. We have a pretty well-stocked pantry, a good number of leftovers in the freezer, and lots of extra meat in the big freezer. Dairy and produce would be a challenge, but I bet we could do it.
When the hubs and I were first married, we had No Spend Wednesdays. It was a good way to make sure we were purposeful about our spending. We got out of that habit, but maybe it's time to start it up again.
Look for some interesting menu planning ahead...and yes, that really is my pantry last summer. It's a bit more crowded now and has less processed food...or cleaners.