NutShellMail - both OutTwit and Twittermail allow you to tweet by email, the later will also email you any direct messages, replies and timeline (on request). NutShellMail does a similar thing but, rather than emails of new followers as they happen like TwiMailer and Topify, it gives you a handy snapshot or digest of your activity (latest followers, quitters, replies, and tweets). Like Topify (above) you can email reply to direct messages.
tweetworks - create or join a group on Twitter. Unlike twitter hashtag channels, you have to join a group first. All tweets to this group are displayed on the group page, see more on Twitter groups. Not sure if I would like to see this on Twitter; I think this would take away some of the magic. The reason Yammer Groups are handy is that you can limit usage to your team or work on a task.
PleaseRT.me - if you want a tweet heavily re-tweeted, enter it into the PleaseRT.me box and it will send your tweet, along with a link in the tweet to easily retweet it. Then you can go back to PleaseRT.me and check out the stats to see the number of times it has been retweeted.