It is very important that you teach your children the value of work and money and helping around the house is an excellant opportunity to do just that. My seven year old daughter has a chart hanging on the kitchen door that lists her chores - cleaning her room, clearing her dishes after she eats, picking up her toys from rooms in the house other than her bedroom, and making sure all her shoes and pieces of clothing are put in their proper places (the closet, drawers, or hamper). At the end of each day we decide which ones were done and she gets to put a sticker on the chart for the ones that were. After she has earned 14 stickers for each chore listed she can get a special treat from the store. If she does extra things around the house like water plants or help walk the dog she gets an extra sticker than can be applied to any of the areas she is lacking in. We have a set limit on how much the treat can cost but if she wants to work towards a bigger one then we negotiate for how long she will have to work to earn it.
My friend has a few children and she can't afford to get them all treats for their chores so they do it as a competition and whoever gets the most stickers is the one who gets the reward. I know it works well for them because the children are always trying to think of new things they can do so they can win.
Another way I keep more organized is by knowing how much stuff is controlable. My duahgter has bins in her room for different catagories of things, a bin for dolls, a bin for shoes, a bin for toy dishes, everything has a place designated for it but it is an easy system for her to manage. then, to keep it at a controlable level we have the rule that whenever you get something new you have to get rid of something old. It helps them to prioratize what is most important to them and keeps toys from overrunning the house. The items she decides to get rid of we either donate or dump which also helps to show her the importance of helping others who are less fortunate.
Or you could try what my mother did, anything left out and you got a waring to pick it up, if you didn't and she saw it again it went in her plastic bin at the top of the closet where you could either buy it back from her or it was goen forever.