Tweet It In is described as 'Save time by compressing Tweets with Tweet It In. It works by automatically abbreviating words, forming contractions, replacing ascii doubles with unicode singles, replacing words with symbols, removing vowels from long words, and shortening urls all as you type in real time!' and is an website. There are three alternatives to Tweet It In, not only websites but also apps for Android and iPhone. The best alternative is TwitLonger, which is free. Other great sites and apps similar to Tweet It In are Twishort and 5Tweets.com.
TwitLonger is a simple service that lets you post those tricky messages on Twitter that really do need more than 140 characters. Write what you need on TwitLonger, and the website posts the link to Twitter for you.