I will cover a few areas that seem to plague most families, homeschool in particular.  We unschool, so teaching-related questions are not here, I will just tell you don't stress over curriculum because you don't need it, don't start too soon and don't push, kids learn what they need to when they need to.

What about chores?
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My library books are taking over my life.

If you are like most homeschool families I know, you have anywhere from 12 to 50 library books in your house right now. How can you keep them organized, used, and back on time? Print out a calendar and tape it to the side of the bookshelf or fridge. Mark when the videos are due and when the books are due with a V or a B and the library name in the square. Next to it tape the printout of items, adding any card checked books. If your library still does not offer this, just take a few minutes to jot down the titles on an index card. Next, put ALL the books in a single place and have a second smaller basket or bag to return books to. Pull and use the books as you need them, return to the place or put them in the 'return' basket. Once you are getting ready to leave to return books, quickly mark off the titles you are returning from the list.
I use a certain bookshelf to hold all the books and a collapsible mesh cube for returns and running back and forth to the library. If you use more than one library system, just double the return baskets, but there is no reason to have 2 separate areas to store them while being used. Show your kids how to check for which library the books go back to.

My art supplies are spilling out of the cabinets.

My favorite dilemma: We have too many art supplies! Get a bunch of plastic shoe boxes at any dollar store or Wal-Mart and start breaking down what you have into smaller sections. You can then arrange the boxes on shelves, stack them in a bigger Rubbermaid bin or marvel at how many sequins you bought 3 years ago SO certain you could think of 20 things to do with them and have a week-long art party and use up supplies that are not vital to basic art. You will always need crayons, glue, scissors, markers, poster paint, a good set of brushes and pencils and stacks of paper. You do not need an entire cabinet of feathers, googly eyes, pompoms, wooden shapes and glitter. Special projects DO use these items and you can buy exactly what you need when you need it. Resist the urge to buy 500 popsicle sticks just because they are on sale. I can attest to the fact that one spilled jar of glitter takes a whole year of regular vacuuming to get up completely.
Put your basic art supplies where you can get to them daily, and more importantly where your kids can get to them.

What about different age-levels and organization?

If you have a child in diapers, one in elememtary school and one getting ready for college entrance exams, you have a variety of needs that must be met. Even just 2-3 different grade levels can be a challenge. The oldest and youngest can take the brunt of the cull in this situation. Make sure of three things as you get started:
Do your kids have too many clothes? This makes for horrors in keeping the laundry done and things put away. Your child needs 5-6 changes of clothes for each season and 2 shirt and pants spares that you can pull out when the knees are gone or there was one too many spills on that t-shirt.
Does your child have too many toys? Do they play with every toy they have and can they put it where it goes at the end of the day? Cull, store, sell, donate until you have just what they need. For more on what kids actually need for toys, check here.
And finally, do you have enough shelves? Put shelves in the hall, in the kitchen, in the bathroom, in closets, line the walls! If every room in your house does not currently house a set of shelves, you are doing something wrong. Can you install a narrow shelf close to the ceiling for a beloved collection and free up reachable space on other shelves?

Next, start culling. Toss, sell, give away or store EVERY item that is not used at least once a week. Exceptions to this are dress clothes for big events. If you are not using it, it is in the way. If your kids only drag out the race track once a year, it needs to go. If they have a REALLY cool/expensive toy that never gets used, put it on eBay. If they have more clothes than they can ever use, start a donation box. Start with the seldom-used and un-loved things. Move all the way to the very used and much-loved things. Don't throw out the snuggy bear, but those jeans that went through every kid in your extended family can go. If you HAVE to save an item because they loved it SO much-that faded red t-shirt he wore every day for the entire summer-put it in a keeper box and consider making a quilt. Make sure their closets and dressers do not harbor any out-of-season clothes, clothes that are still too big or clothes they never wear even if they do fit and were on sale.

Once their rooms are cleaned out and organized, pick and stick-pick a single toy or limited items that will grow with your child-Brio, Imaginext, dress-up, musical toys, science toys, certain books or dvd's, dollhouse furniture or other toys that can be collected and enjoyed for several years. Each October, write up a list of sizes and types of clothes and toys that are wanted and add any family memberships you want to the zoo, science center, botanical gardens...and pass it out to family members, or if you can't be that tacky, keep a list handy for those calls that will be coming in. Christmas is the easiest time to lose control of space! 5 new toys that don't work together or with any other toys you already have is 5 new things that you must make room for or get rid of, and that's money wasted for someone.
If you do have a huge span of ages and abilities in your house, just keep culling, keep it simple, don't buy what you don't need and remember that 5 year old can't use a 500 piece Lego set if the 8-month old is crawling around-make sure you don't make more work for yourself and you CAN say no, return things, give them away, put them up, sell them or loan them out until you can use them.