Hello packing cube! Where have you been all my life?
Seriously, packing cubes can make all the difference. They keep you organized, compact and when Mr. / Ms. TSA pops your suitcase open, none of your stale skivvies will be doing a walk about on the TSA table.
I use the set from Eagle Creek. However, there are many makes, models and price ranges to choose from. I recommend looking for ones that are light-weight, but also very durable. I have used this particular set for several years now, and they still look brand new.
I chose this set because they weigh next to nothing and came in a set of three. I use the small one for my undergarments as well as my PJs, the medium one for all my tops, and the large one I use for pants and sweaters or heavier bulky items.
If you have been looking at travel sites, I would bet that you have heard more than one person brag about their packing cubes. I can tell you, they are worth bragging about.