I don't follow any portal or sites (except of this one) because ones i saw are fulled with pseudo scientists full of great idea, and none of the useful stuff.
But on youtube there are some amazing technical minded people and i recommend
Electronics:
-The Post Apocalyptic Inventor
-mikeselectricstuff
-ElectroBOOM
-lasersaber
Mechanical stuff:
-colinfurze
-AvE
-Engineering Explained
-jimmydiresta
Physics:
-DrPhysicsA
applied physics:
- Applied Science
All those i mentioned above are source of interesting information and you have chance to see a lot of things you probably wouldn't find in your everyday occupation.