I use a combination of packing cubes and packing folders to organize my bag. I have the Eagle Creek packing folders in 15", 18" and 20", but mainly use the 18". The packing cubes I have in medium, large, and slim. I got my original ones at Ebags, but then later found some much cheaper at TJ Maxx of all places. I put about 10 pairs of panties, plus a nightgown in one of the slim cubes and usually have some room left over as those cubes seem to stretch alot. I then use another for a 10 days worth of bras. In a medium cube I put a swim suit, coverup, deodorant, Body Glide, bath salts, and basically anything small that I don't want loose in my bag. I really like the packing folders better than the cubes. A 18" packing folder fits perfectly on one side of my Heys carry on and holds about a week's worth of shorts and t shirts. Use the packing guide that comes with each folder and those things will hold tons. You can really squish stuff down and then they are secured with four flaps woith heavy velcro.
May 2009 I spent 8 nights/9 days at WDW, did carry on only, did not have to wash clothes, carried a skirt and two sundresses, 9 pairs of shorts, 10 t shirts/tanks, underclothes, two pairs of flip flops, sandals, swimsuit, coverup, cell phone, camera, charges for both, and all my toiletries. I had a 15" packing folder in my personal item, a 18" packing folder, two slim cubes, and one medium packing folder in my carry on. My carry on easily fit wheels first in the overhead bin and the personal item was under my seat. No way would all of that have fit in my bags without squishing into those packing folders and packing cubes. I am always shocked at how much stuff you can squeeze into them. I used to use the vacum bags, zip lock bags, and also used to roll clothes. Since using the packing folders and cubes, I can't imagine packing without them. They keep your bags very organized, make repacking a breeze, and your bag will hold ALOT more. I also like that when I get there I can get the cubes that have my underclothes in them and just drop them into the drawers and my clothes don't have to touch drawers themselves.