sink time - this only works if you have a sink near where you school, which I am fortunate to have! I have a small tub with water toys that is kept under this sink, and a stool so she can play in the water
bean play - this has been a great entertainer - though if you have little crawlers you need to be careful about the choking hazard. I got a shallow storage box (like the kind for storing clothing under the bed) and filled it with dried pinto beans (courtesy of the Y2K stash!). I also put some plastic measuring cups and spoons, a shovel and some bowls for mixing, stirring, measuring and pouring beans. She can pull the box out herself now, and plays in the floor, then one of the older ones gets the job of sweeping or vacuuming beans. Much easier to clean up than sand :)
bubbles! - again, you have to have the right set up - we have a door off our school room that opens onto a patio - and windows all the way across, so I can let my 3 year old sit on the patio and see her the whole time. We have a box of bubble paraphernalia - and it keeps her entertained for quite some time.
activity boxes - I have 6 small boxes I filled with things that only come out during school. One is full of sticker sheets, paper, scissors, stamps, etc. One has a Mr. P*tato Head set, another contains a lot of little "happy meal" style toys. I filled a box with play doh and sculpting tools. One has "crafts" - pom pom balls, felt, pipe cleaners, glue, sequins etc. The last one contains the Fisher Price Let's Go Fishing Game - her favorite.
other items to have on hand to entertain a 2-4 year old
bean bags - with a box to throw them into
large beads to thread onto laces
large set of plastic jacks
felt story books - I had some of these from my teaching days, and my kids love them - many teacher supply places carry them - they are story books of familiar tales (Goldilocks, Red Riding Hood, Hungry Caterpillar) with felt pieces to put on the pages to tell the story (there are no words in the books) They are wonderful for second language instruction (that is why I had them) but they also are just plain entertaining. They are a bit pricey, but would make a great birthday or Christmas gift.
I also have a file box of Zipl*c bags with a variety of homemade activities (sorting, matching etc. ). Many of these ideas can be found at Paula's Archives.
Another great find was a water play station from K-Mart - it was on clearance and cost under $30 - a great birthday present for grandparents to give!Finally, something I learned from MOTH: I have certain times during the day when an older child is assigned to play with a younger child. Both the older ones take a turn with the baby during the day (20-30 minutes), and they also each have one on one play time with the four year old. This is probably the biggest help. So when I know I need 30 minutes of time with the crocodile hunter, the little princess plays with her little sister during that time. Then they can trade off. Not only does this help me, but it encourages them to spend one on one time with each other.
Well, you have read my ideas, now share some of yours - if you have a great way to keep your toddler busy, leave me a comment with your idea or a link to your blog with ideas. I am always looking for more!