Hashtags are just an easy way to create in your tweets hyperlinks to search terms. But some people really hate to read hashtags (#especially #when #abused) because of their odd appearance.
#HashMeNot will remove the hash sign in every hashtag. Also it will convert mixed case hashtags to a more readable form. For example "#SomeMixedCaseHashtag" to "Some Mixed Case Hashtag".
Google Chrome version available here.