How many times in total has Earth formed a super continent?
According to a review by Nance &amp; Murphy (2013), there are five known supercontinents, from the most recent to the most ancient: 


Pangea (of course)
Pannotia (though it depends on how you define supercontinent), ca. 600 Ma
Rodinia, breakup at ca. 750 Ma (see e. g. Torsvik, 2003)
Columbia (also called Nuna), ca. 1.6 Ga
Kenorland, ca. 2.7 Ga


Some additional ones such as Vaalbara in the Archean are still mostly speculative.