This site provides 24 hours of historical data on hashtag searches, as well as more in-depth data and analytics for paying accounts. Useful for top-level overviews of the popularity of a particular tag, you can use this tool on a daily basis for a week or two to find out how much love a particular tag gets over a longer period of time.
This site also allows you to search for terms and see popular links shared on twitter related to your search along with their related hashtags underneath. This can be useful both for searching for tags for your own content and for competitive analysis.
Tweetreach is useful for providing top-level insight into the effectiveness of the tweets that you’re hashtagging. It allows you to search for hashtags or other search terms and returns to you the number of accounts reached, the number of impressions for that particular search for the first 50 mentions it finds of that particular term. In order to access all of the data,