What kind of spider is this from Nova Scotia, Canada?
That is an Araneus diadematus, a kind of garden orb-web spider.



Orb-weaving spiders are quite common, and can be found nearly anywhere in the world, excluding Greenland. The following is a distribution map for the species A. diadematus, of which, as you can see, is mostly contained to North America &amp; Canada.


Dark gray: present; Light gray: no record. (source)