SDL2 and C++ Video Tutorial Series: A YouTube series of videos showing how to setup SDL2 with C++ and various other beginner to intermediate level topics on using SDL2.
SDL Haptic in depth (Archived): Covers the basics of how to create and playback simple force feedback effects with SDL
Input
Text Input: Using SDL for text inputs with specific consideration for international users.
Threads
Condition variables in SDL (Archived): A good discussion of condition variables (in computer science rather than gaming context), some mention of mutex and semaphore use.