Further Resources

www.instagram.com/edified.architecture/: features a follow list of approximately 1,000 of the best architecture-related accounts. 

https://www.flickr.com/groups/architecturedirectory/: features an unparalleled collection of categorized photo sets.

https://www.reddit.com/r/architecture/wiki/index/: the "top posts of all time" sort feature can be especially helpful.