As of 2016, some free squirrel trap plans include the trap anything plan and a PVC tubing trap. Plans for both of these traps are available online at Trap-Anything.com.
The trap anything plan is a design to create a box trap that captures squirrels and other living animals. This plan only requires three pieces of wood to start. Pictures of each step are included with all the written directions.
The PVC tubing trap plans is as simple as using a length of tubing and capping off one end. This trap relies on the slippery insides of the tubing to trap the squirrel who goes in after food left as bait. There are couple of included tips to make the trap more successful.