21LTRhttp://21ltr.com/scenes/
Damn Vulnerable Linuxhttp://sourceforge.net/projects/virtualhacking/files/os/dvl/
exploit-exercises – nebula, protostar, fusionhttp://exploit-exercises.com/download
heorot: DE-ICE, hackerdemiahttp://hackingdojo.com/downloads/iso/De-ICE_S1.100.iso
http://hackingdojo.com/downloads/iso/De-ICE_S1.110.iso
http://hackingdojo.com/downloads/iso/De-ICE_S1.120.iso
http://hackingdojo.com/downloads/iso/De-ICE_S2.100.iso
hackerdemia – http://hackingdojo.com/downloads/iso/De-ICE_S1.123.iso
Holynixhttp://sourceforge.net/projects/holynix/files/
Kioptrixhttp://www.kioptrix.com/blog/
LAMPSecurityhttp://sourceforge.net/projects/lampsecurity/
Metasploitablehttp://sourceforge.net/projects/virtualhacking/files/os/metasploitable/
neutronstarhttp://neutronstar.org/goatselinux.html
PenTest Laboratoryhttp://pentestlab.org/lab-in-a-box/
Pentester Labhttps://www.pentesterlab.com/exercises
pWnOShttp://www.pwnos.com/
RebootUser Vulnixhttp://www.rebootuser.com/?page_id=1041
SecGame # 1: Sauronhttp://sg6-labs.blogspot.co.uk/2007/12/secgame-1-sauron.html
scriptjunkie.ushttp://www.scriptjunkie.us/2012/04/the-hacker-games/
UltimateLAMPhttp://www.amanhardikar.com/mindmaps/practice-links.html
TurnKey Linuxhttp://www.turnkeylinux.org/
Bitnamihttps://bitnami.com/stacks
Elastic Serverhttp://elasticserver.com
OS Boxeshttp://www.osboxes.org
VirtualBoxeshttp://virtualboxes.org/images/
VirtualBox Virtual Applianceshttps://virtualboximages.com/
CentOShttp://www.centos.org/
Default Windows Clientshttps://www.microsoft.com/en-us/evalcenter/evaluate-windows-10-enterprise 
https://dev.windows.com/en-us/microsoft-edge/tools/vms/
Default Windows Serverhttps://www.microsoft.com/en-us/evalcenter/evaluate-windows-server-technical-preview
Default VMWare vSpherehttp://www.vmware.com/products/vsphere/