Command line
SS64 Forum
DosTips
PowerShell forum

Tools
Google Translate
Google Trends
BitLocker keys
Conversions
Passwords
PortCheck
Regexr
ScreenCapture
Stylish

Web Testing
Downdetector
Down4All / Just.Me
Color Management Test
G Suite Tools (MX, Dig, SMTP)
JustDelete.me
NetCraft tools
SSL Labs
VirusTotal

Blogs
EFF deeplinks
Schneier

Tech
Arstechnica
HackerNews
OSNews
TheRegister

Zeitgeist
NewsBlur
PopURLs
Tumblr
Waxy
XKCD

email
Gmail – basic
Calendar
Outlook
Yahoo / FastMail
Doodle / Trello

Music
Bandcamp
Steve Hoffman forum
Radiolab
DR Database / LdP

Courses
Harvard / MIT / Yale
duolingo / Codecademy
Coursera / Udacity / Edx

News
Google News
NY Times
The Guardian
New Yorker
BuzzFeed
NPR

Shopping
Amazon:
Books, DVD,
Music, Deals

Ask Metafilter
KK Cool Tools
PC Keyboards
TheWirecutter

Travel
GoogleFlights
Kayak
Rome2Rio
SeatGuru
OpenTable

Maps
Google Maps / MyMaps
Open Street Map
Bing maps
Mapcode - app
Dark Sky - weather

Search
Duck Duck Go
Qwant.com

Google / ncr
GoogleAdvanced
history/activity/ads

Photo/video
Flickr
Golden Hour
Photo.net
Vimeo
YouTube

File/Photo sharing
Box
imgur
Hastebin
Send.Firefox
SendSpace
WeTransfer

Reference
Wayback Machine
World Time
Wikipedia