Twitter Friends is a nice free social extension for Joomla with which you can display your Twitter Friends and Followers on your Joomla website. Theo van der Sluijs, the author, realized it with a fast loading source code. You can download it via GitHub. It works with Joomla 2.5 and the earlier editions, Joomla 1.6 and 1.7.

Save bandwith with Lazy Load for Joomla! by Viktor Vogel. This free performance extension for Joomla loads only all images of your website, which are situated in the visible area of your website. So this tool is especially helpful, if your website includes a lot of pictures. The configuration is very easy and can be manage directly in Joomla Backend. You can also exclude images, components, URLs or Bots. A nice fading effect makes this plugin to real eyecather. The download is free. Lazy Load for Joomla! works in Joomla 2.5 and Joomla 3.0.

With Mootools Enabler/Disabler, you decide, if Mootools will be loaded on your website, and that saves up to 600 kb bandwidth. Although it is included in the Joomla package, you don't needed in most cases. The installation and handling is very easy. You can add all components, which use Mootools, directly in the plugin manager and disable it for all other. The download is free. Mootools Enabler/Disabler is native to Joomla 2.5 and Joomla 3.0.