Paddling.net is one of my favorite sites for paddling info. They have a periodic boat giveaway, photos, and some very good writers.

This article about strainers caught my eye because not too long after I started paddling regularly my son and I were in a tandem kayak on Eagle Creek and got caught by a strainer right after a sharp bend. It was November, so the water was very cold, and weren't far from the takeout, but wrestling a swamped boat out of the water in cold temperatures isn't fun.
We were fortunate that we just dumped the boat and floated on through the branches, but strainers can be very dangerous and are something to be on the lookout for, especially on smaller streams where you may not be able to see very far ahead.