Sites I’ve come across that are really good resources and have helped me accomplish tasks within my own lab and other scenarios:
VMware
Virtu-al.net – PowerCLi VMware scripts
Networking
Ping.eu – Network & DNS checker
Network-Tools.com – IP, DNS, & Blacklist checker
Cisco
CiscoQuickLinks.com – Any documentation and downloads Cisco related can be found here
Microsoft
4sysops.com – MS news and tutorials
Joeware.net – Anything AD related
DependencyWalker.com – Application Dependency mapper
MXToolbox.com – SMTP testing tools
msexchange.org – MS Exchange blog
Security
instantssl.com – Free 90-Day SSL Cert
LetsEncrypt.org – Free 90-Day SSL Cert
Blogs
Yellow-Bricks.com – VMware vSAN Blog
Blogs.VMware.com – General VMware Blog
VirtuallyGhetto.com – VMware Blog
RobPickering.com – General IT blog
Laurence.id.au – General IT blog