TwitterBar allows you to post to Twitter from Firefox's address bar. A small Twitter icon sits to the right of your address bar; clicking on it will post your tweet, and you can hover your mouse over it to see how many characters you have left.You can also post by typing "--post" at the end of your tweet. Clicking the Twitter icon when visiting a webpage will send a tweet containing the URL of the webpage you are currently viewing.
You can also download TwitterBar here or directly from www.chrisfinke.com.
