Nagaraj Venkatesh I started a list which is by no mean exhaustive (also available on technet forums : https://social.technet.microsoft.com/Forums/en-US/b74d3c8d-f55b-4781-9999-198a57da0bd4/saving-the-blogs?forum=operationsmanagergeneral )
I fully understand most of these were not from product team or engineering, but they still had enormous amount of very useful info and their loss has already caused me some trouble while searching for stuff that I knew was there!
- https://blogs.technet.microsoft.com/momteam/ > still online, (more or less) moved to https://techcommunity.microsoft.com/t5/System-Center-Blog/bg-p/SystemCenterBlog/label-name/System%20Center%20Operations%20Manager
- https://blogs.technet.microsoft.com/privatecloud > offline, didn't find a new url
- https://blogs.technet.microsoft.com/germanageability > offline, didn't find a new url
- https://blogs.technet.microsoft.com/kevinholman/ > https://kevinholman.com/ (of course!)
- https://blogs.technet.microsoft.com/kevinjustin/ > still online
- https://blogs.technet.microsoft.com/allthat/ > still online
- https://blogs.technet.microsoft.com/lukaszr > offline, didn't find a new url
- https://blogs.technet.microsoft.com/manageabilityguys/ > still online
- https://blogs.technet.microsoft.com/nathangau/ > still online and has a new url as well : https://nathangau.wordpress.com/