My favorite one in particular is "Where To Travel & When" because Justin and I spend a lot of time trying to figure out where to travel based on the time of the year that we want to go. And I truly believe that it is so important to have knowledge of what the weather is like during various seasons, when certain festivals or holidays are happening, etc. so you can plan properly.
A perfect example of this was our trip to Japan, which was amazing but it was just so hot, humid and sticky the whole time we were there because it was the beginning of typhoon season. And we actually knew that it wasn't going to be the most pleasant time of year weather wise to visit when we planned the trip but Justin really wanted us to go in August because he wanted to go to a Japanese baseball game. So we had to take all of that into consideration when we were planning and packing so that we were properly prepared, which we thankfully were.
Another illustration that I really enjoy is their "How To Plan A Foolproof Itinerary" which is something Justin and I are constantly striving to do when we're planning a trip (You should see the spreadsheets that Justin makes before we go on vacation. They are incredible. So much so that we've contemplated selling the one he made for Iceland and Amsterdam because people are constantly asking us for it), and a lot of the tips that they mention are actual things that we do when planning our travel itineraries.
For more of their travel illustrations and tips, you can visit the Fix.com article which was written by Nicola Brown.