Where can I find a full list of dungeons?
Here's a list of the clearable locations on UESP.
And I like this map to find them all.
These are all the locations in Skyrim. http://www.realsg.com/2011/11/guide-skyrim-complete-locations-map.html
I've counted over 530 locations. I would say there is definitely 130 or more dungeons.
I believe a dungeon is cleared when you kill every enemy within the dungeon. There may be an undead on a wall behind a locked door, or a passage that was hidden well. Check your dungeon map when re-exploring.