For the kids to be entertained, since they are so young, think about their senses--things they can touch: water, sand, blocks, different places to see, different sounds...smells...Just some water to splash can be a lot of fun! Also listen to music, dance and sing--for them or for you. If you want grown-up music, use an ipod.
You can go to museums if you can afford it, but you can also do things at home, in the park, in the backyard, on a walk and so on. Little trips can help break up the day, but if your kids are a lot of trouble to travel with by car, then you can just walk to places nearby, for a change of scenery.
You can put a tent in the backyard or in the living room, if it is a small tent (that can be fun for young children).
If you need some adult company, try to arrange playdates with other parents, or call friends and ask them to visit.
If your kids nap, and you have time or you feel bored, you may have time to do some reading. If not, try a book on cd and you can listen while you clean house or drive on errands.
For organization, don't put to much pressure on yourself. It is hard to clean with kids.
One secret I have learned is that less STUFF means less MESS!! Keep your house simple. More decorations, toys and clothes mean more time cleaning, more mess...and less space.
Also, try to make fewer steps to your cleaning: don't put any dishes in the sink or on the counter. Put them straight into the dishwasher after they are used, and be sure to empty the clean dishwasher as soon as you can, so that you are ready for the new dishes.
When you do laundry, keep everyone's clothes separate! Wash/dry just ONE person's clothes at a time, and then you can put them away in just one closet, without having to check which clothes belong to whom, or having to make different trips to all the rooms to put them away.
Cook simple things--not a lot of ingredients, not a lot of chopping, not too many mixing bowls or pots to wash...
I like to keep a "dish brush" (scrub brush with a handle) in each bathroom so that I can brush out the sink whenever it starts to look spotted.
When you think of something you need, write it on your shopping list right away, or you may forget, and that means extra trips to the store.