Years ago Lincoln Welding had a newsletter called the Stablizer. I do not know if they are still sending them out but they have several project ideas. You might try their site http://www.lincolnelectric.com/community/projects/ and see if any of these might work for you.

I always liked to build t-post drivers- they are thick so the kids can arc weld easily

1- 2 1/2 " ID Pipe 28" long

1- 2 1/2" rod plug -- 4" long

2- 5/8" HR rod for handles -- each 20" long

You will slide the entire plug down into the pipe so that the pipe sticks up about 1/2" over plug- that way the kid can weld all the way around the inside of the pipe. I figured even if the weld broke, they will still have the entire bead on the inside of the pipe to keep plug from popping out.

I bent the handles in a U- shape with a torch- about 4" on each end. Be sure to check that they are not twisted!!!

I usually tack the handles on so they were straight.

I also experimented with 3" rod (because I had some) welded on top of the pipe and that works ok too.