Tin toys are often made of recycled materials like coke cans or other tin cans. There are some safety measures to take when working with tin. Most of these projects are appropriate for adults or kids that are at least 10 years old.
Learn more about tin toys here.
The Pop Pop Pages
Here's some more general information and on these pop pop boats. There is history, explanation of how they work and links to making instructions.
Make a Ponyo Pop Pop Boat
Go to the page
Make a Giant Tin Toy
Have a look here
Altoids Tin Crazy Car
A rubber band powered tin car. This is a fun and fairly simple project.
Coke Can Shark
Visit the page.
Randy's Toy Shop
I found this link interesting although it doesn't contain guides to make any toys.
Randy's Toy Shop restores and sells very old-fashioned toys, mostly made of tin. If nothing else, have a look at the pics on the site.
Making Tin Can Toys
The book is quite old (1919) so it's not the easiest to read neither is short and quick read. But the details and information is really good.