Gramfeed.com allows you to search any hashtag on Instagram. It also shows a map for the geotagged Instagrams. You need to login first.
At
Tagboard.com you can search hashtags and visualize posts from various social media (Twitter, Instagram, Facebook).
Storify and Padlet allow you to bring together all the posts and other media along with text.
Search for the meanings of hashtags at
Hashtags.org. This is especially useful for current events and world issues.