Starting Stretching is a basic stretching routine for overall flexibility. Beginners should start there.
Experiencing pain in your neck/shoulder/back/hips/groin/legs/knees/ankles when you run/walk/sit/squat/stretch? Go see a doctor! Stretching may not be the solution to your pain!
This toe-touching routine was used for the 30-day challenge with great success.
Can't touch your toes? Try this toe touch progression (why this works).
This Side Splits Test will tell you if you have tissue or hip structure limitations preventing you from achieving the side splits. Here are the rest of the articles in that series. Worth reading if the splits is your goal.
This splits routine was created for the 90-day challenge.
Hit a plateau in your splits training? Try these brutal but effective loaded progressions. here and here. Oh, and here.
Starting Stretching is a basic stretching routine for overall flexibility. Beginners should start there.
Tim Hall's flexibility training material has more advanced information and uses dynamic and isometric/PNF stretching methods.
Tricks Tutorials: Developing Flexibility has more information about dynamic and isometric/PNF stretching.
Kit Laughlin's Youtube channel has great stretches paired with clear instructions to do them properly.
'Flexibility Friday' archive from r/bodyweightfitness
Mobility WOD has a lot of information but can be difficult to navigate.
Doug Richards on the science and fiction of stretching
Stretching and Flexibility by Brad Appleton. A classic resource on flexibility training.
Emmet Louis explains Loaded Progressive Stretching