Opengl-Tutorial

This website is great for learning the basics. They have a wide range of beginner to intermediate level tutorials. The best part of this website is the tutorials are provided in OpenGL 3.3 and 2.1. You can view the source code here and to change OpenGL versions, just change the branch to the appropriate version.

See Opengl-Tutorial.org

Misc Tutorials

Interleaving VBO
Textures Explanation
Frame Buffer Objects (FBO) Example

Beware of OOP in game development!

Approaching game delopement runs into multiple issues with handling game objects. Inheritance will slowly become a nightmare. Read this article for a professional's perspective of why ECS (entity component systems) are better suited for games.

See Evolve your heirachy on reasons to use an ECS

ECS Examples

Here are several examples and articles explaining how ECS work. Note - There are several ways to implement an ECS

Entity Systems Wiki - massive compilation of ECS info
ECS in MMO Development
Fast Entity Component System Example
ECS Tutorial

Freetype2 Font Engine

Freetype2 is supposedly used by Blizzard. It's an open source font engine. It's not necessarily the easiest engine to use but is very powerful.

Freetype Website
Implementing Freetype into OpenGL
    Note - Follow the source code instead of the "outdated" article code
Freetype2 Wrapper: FTGL
Freetype2 Wrapper: OGLFT
    Note - The wrappers are nice and will make your life alot easier. However, they are coded in old OpenGL and you lose shader control if that matters to you.

FMOD

FMOD is so far the easiest sound library I worked with. One downside with FMOD is it is proprietary. However if your budget is under $100k then your can use it for free (on your first title). There are plenty of examples and information provided in the download to get you started!

Bullet Physics

Bullet Physics Engine was the most appealing open source engine. It supports multiple features such as convex hull support, multi-threading, and OpenCL.

One "disadvantage" with Bullet is the documentation is lacking a little. The API isn't well documented and most of functionality has to be learned through the provided Demos.
Bullet Physics
Comparison between ODE and Bullet
Games using Bullet

Math Library: GLM
DDS Texture Loader: GLI

Sound Database
3d Models
Skybox