Twitonomy - Twitter analytics and much more.
hashtags.org - Hashtag is an extensive hashtag research platform for analytics and tracking of hashtags, providing...
HSHTG - Generate, manage, save and edit hashtags just in a few finger tap
RiteTag - No idea which hashtags to use? Get instant hashtag suggestions for images and texts on desktop and mobile.
HashtagWiki.com - Hashtag Generator Tool
What the Trend - What the Trend does analytics of trending subjects like hashtag analytics