What are the canonical texts for the Buddhisms of the world? And as a follow up, what institutions are charged with expanding the list of canonical works, if any?
For Theravada there is the Tipitaka: http://www.accesstoinsight.org/tipitaka/index.html

This consists of the "three baskets"  of the vinaya pitaka,  the rules for monastics,  the sutta pitaka aka the sutta teachings,  and the abidhamma. 

It is generally accepted that the oldest and most core part of the Tipitaka that is closest to what the buddha said,  are the four Nikayas

Digha Nikaya (long discourses) 

Majjhima Nikaya ( middle length) 

Samyutta Nikaya (grouped discourses) 

Anguttara Nikaya ( numbered discourses) 

There is also the Khuddaka Nikaya which is a collection of "little texts".  This is where the famous dhammapada  and Sutta Nipāta reside.