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.
I'll add the other part of the answer:
Tibetans take the Kanjur to be canonical. It's is a huge list of documents. New documents are added as new terma are discovered. Terma are roughly teaching left long ago to be discovered today.
The Chinese Buddhist canon was compile a long time ago. It also is a hug list of documents. As far as I know, there isn't an institution to expand it. I would guess the natural role would be the Chinese Imperial Government, which doesn't exist at the moment, or at least is hostile to Buddhism.
The Pali canon, as mentioned by Jayantha is a huge set of documents and as far as I can tell, there isn't any institution that is attempting to add more text to it.
Just bear in mind: Different traditions will give you different answers, theravada and mahayana traditions have different suttas, the same thing goes for the commentaries and the importance of later works... Nevetheless most of the suttas and the Vinaya are the same.
I always use tipitaka as a reference and I like to read the 4 nikayas (Im a lay person)
Nothing can be added to the list of canonical works of the Buddha. They were recited three months after the Buddha's parinibbana and cannot be added to or subtracted from.