Automate your activities on line using "If I do this, then do that with it' formula. Example: if "I tweet", then "post to Facebook." This is very helpful for those who use multiple social media networks or just want to make archiving some of your online tasks easier. Free right now as it is still in open beta.
My favorite desktop Twitter application. Allows you to group the people you follow to organize the noise. Create lists or use Twitter Lists. Add search columns. You can have multiple Twitter accounts. Also updates Facebook, MySpace, LinkedIn, GoogleBuzz and Foursquare. Allows schedule a tweet in the future.