Below are the different tools and resources that I use and recommend from time to time.

Learning/Training

Books

Podcasts

Online Training

Free

Paid

Tools / Services

Operating Systems

Hypervisors and Virtual Environments

DevOps

Configuration Management

Data Science and Database (Tools only)

Troubleshooting / Datacenter Tools

Monitoring / Uptime

Cloud Hosted Providers

Text Editors

Knowledge Sharing, Note taking, Collaboration

Other helpful tools and general stuff

Web Utilities