Reddit mentions of Residential Energy: Cost Savings and Comfort for Existing Buildings (6th Edition)

Energy efficiency engineer here.

You want diagnostic equipment that's straightforward, temporary, and relatively inexpensive and durable. While there are a ton of diagnostic options for professionals, most of them are not well suited for average consumers because they require more know-how, software, or post-processing to understand.

My initial reaction is that kill a watts are good- they are simple and very easy to deal with, and relatively cheap. Get a few.

The IR camera is useful, but only if you know how to interpret it.

I'd recommend that you get a copy or two of Residential Energy ( http://www.amazon.com/Residential-Energy-Savings-Existing-Buildings/dp/0133418960) since it's written in an understandable manner and is full of really great information.

Do you guys have natural gas? If so, I'd get a gas sniffing wand. Last thing you want is for a well meaning person to seal their house up tight and then have their house explode due to a gas leak that would have never built up in a drafty house.

A pro grade caulking gun might be helpful- most people would never buy a nice one but they make the job much better.

Get an IR thermometer gun. It's a much faster way to check surface temperatures, which could be used by somebody who wants to do some math about heat loss calcs.

I'll think some more and see if I can come up with other simple tools. Honestly, the best thing to do is get a professional energy auditor, but you can't really get one of those to keep at the library...