We're trying to sell our house and plan to move soon, 3rd time in 3 years. Bleh.
I am just now (9 weeks postpartum) starting to seriously declutter, throw out, get organized again. Actually we don't have that much stuff because even though we moved from a 2 bedroom apt. to a house, we didn't buy much furniture. We have a lot more toys. Many of them are going on a secret permanent vacation.
One thing I have done is organize all the kids' clothes not currently in use in those big clear plastic rubbermaid boxes by size and gender. This way if my sister in law gets pregnant and wants them I can just give her what she needs; when my oldest daughter outgrows a season/size it goes in the box for my second daughter, I can put my hands on stuff to sell/trade, and I know what I have so I don't buy more than I need. Also it's already ready to move.
I am taking down pictures/decor and wrapping them in old towels and sheets, and cloth diapers that are in the retirement stage. I am also collecting boxes here and there (those big diaper boxes from Costco that the neighbors put out every week find a nice place in my attic...they're very good moving size!...people are going to think we use a LOT of disposibles,
I am freecycling LOTS of stuff. Ruthlessly getting rid of junk. Selling off or donating books not being read, and having been toted around the last seven years through moves and jobs and hopelessly outdated by now.
Now if I could just get dh to stop burying us in scraps of paper...as soon as I create a clutter place for him, he fills it up and starts depositing more everywhere else again.