I highly recommend pentesterlab.com. The Web for Pentester course is a great intro for first timers if you read the PDF and play with the VM

When training newbies I will start with this and get them to play around with google-gruyere.appspot.com.

These are only relevant for web app testing, I haven't been able to find a suitable free resource for network testing but for paid resources OSCP is a great practice course if not pretty challenging for first timers