If you're not familiar with edX, they have many informative and interesting free online courses.
I came across one that really impresses me, and I'm sharing it with you!
I provide both, because I heard about it on edX, and I like edX, but if your focus is strictly on Linux learning, you may just want to go straight to the source.
Anyhoo, about the course, it's very professionally done, and a great introduction to Linux. Topics covered include:
Chapter 01: The Linux Foundation
- Section 1: The Linux Foundation
- Section 2: The Linux Foundation Training
- Section 3: Course Linux Requirements
Chapter 02: Linux Philosophy and Concepts
- Section 1: Linux History
- Section 2: Linux Philosophy
- Section 3: Linux Community
- Section 4: Linux Terminology
- Section 5: Linux Distributions
Chapter 03: Linux Basics and System Startup
- Section 1: The Boot Process
- Section 2: Kernel, init and Services
- Section 3: Linux Filesystem Basics
- Section 4: Linux Distribution Installation
Chapter 04: Graphical Interface
Section 1: Graphical Desktop
Section 2: Session Management
Section 3: Basic Operations
Chapter 05: System Configuration from the Graphical Interface
- Section 1: System, Display, Date and Time Settings
- Section 2: Network Manager
- Section 3: Installing and Updating Software
Chapter 06: Common Applications
- Section 1: Internet Applications
- Section 2: Productivity and Development Applications
- Section 3: Multimedia Applications
- Section 4: Graphics Editors and Utilities
Chapter 07: Command Line Mode Operations
- Section 1: Command Line Mode Options
- Section 2: Basic Operations
- Section 3: Working with Files
- Section 4: Searching for Files
- Section 5: Installing Software
Chapter 08: Finding Linux Documentation
- Section 1: Documentation Sources
- Section 2: The man pages
- Section 3: GNU Info
- Section 4: The --help Option and Help Command
- Section 5: Other Documentation Sources
... There are 10 more chapters.
As you can see, a comprehensive introductory course.
Please have a look!
Update 15 Dec 2017 - I tried signing up through the Linux Foundation and the link referred me back to edX.