A balance board is an incredibly simple toy. You put a board on top of a cylinder, stand on it, then try not to biff it. It is really a fantastic toy for all ages (though my toddler is a wee bit too small). I've even found myself fighting for a turn.
For the balance board itself I don't have a list of materials or even measurements for you. The directions are basically, go look in the basement or the garage and see what you got. The longer the board the easier it will be to balance. The width doesn't matter so much, but your kids should be able to fit their feet on it. As for the cylinder, I started with a piece of PVC pipe, but it was just too high for my kids (perfect for me though!) so I used an 1 1/2 dowel cut down to the width of my board. I couldn't actually find the dowel when I was decorating the board and taking pictures, so what you see above is a block from my kid's toys. What I'm trying to say is, you can make this toy with what you have, all I'm going to show you how to do is pretty it up.
I wanted something on top of the wood to protect my kids' feet and make it easier to grip. Duct tape to the rescue! You could easily just do stripes, but I thought why not make something super stylish instead. To make the chevron pattern, first you have to rip the duct tape into strips. Cutting the tape is almost impossible, so just clip a bit at the end of the tape and then rip it into strips while it's still on the roll. I ripped my tape in thirds, but ended up only using the right and left sides--the edges on the one in the middle were just too raggity to use. So I would suggest just ripping the tape in half. You will waste less (though my son did have a hey day with the extra tape), but the chevron stripes will be much thicker.
The length of your tape strips will depend on how wide you board is. Play around a bit to see how you can make a few zigzags fit just right. For the first chevron stripe, start in the middle and make a V with two pieces of tape, making sure the point of the V is in the center of the board. Now that you've zigged, just zag out to each side.
For all the other stripes, start from the right and work your way across. Put one tape strip down, then overlap the end of that piece with your next piece, as you can see above. Use the manufactured edge--because it's super straight--to overlap a little bit the stripe that came before. Then trim the ends flush with the sides of your board. That's it. Just keep going until you've filled the whole board. This project is a little fiddly at first, but don't worry after 3 or 4 stripes it picks up speed and you'll be wiping out before you know it.
You can decorate the dowel with all the leftover bits of tape. It's not necessary, but it does make the dowel much easier to find. :)
The more I play with this toy, the more I like it. It works inside and outside, it's a good gift to give kids, and it's endlessly customizable. I made another one painted it with a little leftover paint mixed with sand (so it's non-slip) and I have ideas for lots more. So if you know me, you children will probably be getting a balance board for their next birthday. Or I might just keep them all for myself.