If you want add fan box for Twitter similar to Facebook, it is possible thank this module, available in Joomla 1.5 and Joomla 1.6, when someone do click in button "follow" automatically the user will be your follower. Also you can modify the size of width and height to fit in you web, now many people may follower to you.

This module for Joomla 1.5 is special because has validate W3C XHTML code based in CDATA, if you are a strict in the design of your web, but if you have a problem, change the option no validate.