We put bulky clothes under the seats in our pop-up. However, we have 2 sets of storage drawers - the type with 3 drawers. The small one we keep next to the kitchen area, and it holds odds and ends. It is low enough that we place a small lamp on it to provide light for reading in bed!
We have a larger unit that we use for underwear, socks, and a few pair of tee shirts and shorts. This works very well - we don't need to root around for something everytime we need it. The large drawer under a bunk is used for toys, movies, etc. We also keep a couple rubbermaid tubs outside for shoes, toys, and dirty clothes. We also have a 13" TV/DVD player that we enjoy. It goes in our "Teddybear Room" - grandchildren's guest room - when we are at home.
We bought the Coleman Mesa as it has the most storage space. It takes a while to develp a system, but I agree that being organized really makes camping in a pop-up much more enjoyable. Sandie