Puffins are not endangered but they are threatened by human activities and are rare in many areas where they were once abundant. (from the Audubon Society)
Here are a few resources for aiding puffins. It doesn't seem like the concern for puffins is especially high at the moment. Though the UK census results due in July will tell us interesting things about the population rate there.
The National Trust UK is working on its coastlines.
The World Wildlife Fund offers sweet puffin adoption kits.