Eirik's a handy guy:
Two years ago I made a chair for my son that has been very popular. It works fine for years and is quite safe even for kids that can't walk or sit properly. Because of the way it is made your kid will not easily fall out and with the wheels it is a great toy as well.
Recently I had to make another one and of course I did not find my original drawings. Now I have posted the details on my blog for future reference.