I'm with Jo G, I am obsessive about de-cluttering. I do a major overhaul of the entire house, room by room, every 6 months, and in between times I toss anything broken, torn, or otherwise unusable to keep clutter from building up.
With that done, there's not a whole lot of organizing that really needs to be done. I put off-season clothes for DH and me in clear plastic bins, labeled accordingly. For the kids, stuff that has been outgrown and will be passed down, I put in a bin labeled with the size and season (for example, just put away the older child's size 10 winter clothes in a bin labeled with the younger child's name and "Size 10 winter" on the outside). The younger child's outgrown winter clothes went to a smaller cousin labeled with the cousin's name and "Size 5 winter." Off-season storage bins go in the garage on a shelf DH built for this purpose, so it's not cluttering up my house!
Because our smaller bedrooms are super small, I removed the closet doors in the kids' rooms (they had the sliding doors) and put in tension rods (like for a shower curtain), and fabric shower curtains to cover the closet opening. This way, my kids can see their whole closet at once. Then, I put in 2, 5-section sweater hangers and 1 shoe hanger, and put all their folding clothes on the sweater hangers (1 section for socks, 1 for underwear, 1 for dark shirts, 1 for light shirts, 1 for shorts, 1 for pants, etc) and all their shoes are in the shoe hanger. Then I was able to remove the dressers from their rooms, which gave them more playing space, less stuff to clean, fewer drawers for things to lurk in... and of course, all the sections in the sweater hangers in the closet are labeled.
My biggest challenge is mail. I swear it multiplies inside the mailbox. Before I even set it on the counter, I sort through it, immediately toss the junk mail, and then it either goes into the "bills" basket or the "needs to be addressed" basket (such as invitations or DH's work stuff, or things that I need to file in the filing cabinet). Then once a week I pay the bills and file the stuff that needs to be filed, respond to invitations, etc. I keep a book of stamps in the "bills" basket, plus the checkbook and a pen, so it's all in one place and makes the chore less annoying.
But yeah, the biggest thing is decluttering. If I haven't used it in the past 6 months, then I absolutely don't need it cluttering my drawers/cabinets/closets! I actually have 2 closets and several cabinets that sit completely empty (and my house doesn't have a ton of storage to begin with).