I've been doing Virtual Machines from past 4 months. Some of them I've done by myself and some of them were done along with motley crew.
Usually I do writeups for any VM that I solve.
Here's the list of all the VMs I've solved.
Note: All the difficulty ratings are from 10(Obviously) and they are relative, meaning a machine that looked like a 3 to me might be a 1/7 for you.
If you are beginner then you can start with any of the following:
If you want to do OSCP type machines then checkout
There are some machines that might not come under OSCP type
but teaches something really nice are: