In order to demonstrate the use of various Joomla extensions (components, modules and plug-ins), I have put hyperlinks to some of my clients' websites.  Here you will see the extensions in action and configured to the specific needs of each client.

The Image Gallery Component - http://www.theinvinciblestour.org/index.php?option=com_joomgallery&Itemid=201

The Google Calendar Events Component - http://www.aminyaacademy.com.au/events-calendar

The Tabs Page Viewer Plugin - http://www.twra.net/

The Directory Component - http://www.twra.net/index.php?option=com_mtree&Itemid=58
 

The On-line Catalogue Module - http://catswhiskersgiftshop.com/index.php?option=com_virtuemart&Itemid=58l

The Image Rotator Module - http://www.sctimberdoors.com.au/index.php?option=com_content&task=view&id=5&Itemid=6

The Newsletter Subscriber Module - http://www.gccc.qld.edu.au/

The Slider Page Viewer Plugin - http://www.cotedusoleil.com.au/index.php?option=com_content&view=article&id=5&Itemid=7

The Vertical Image Scroller Module - http://www.smartchoicehomes.com.au/

Resonline Booking Script - http://www.mooloolabamotel.com.au/content/view/22/49/ 

The Video Streamer Module - http://sunshinecoastpots.com/media/tv-advertisement

The Header Image Rotator - http://www.sunshinecoastfurniture.com/

StatCounter (third party hit counter) Module - http://my8.statcounter.com/project/standard2/stats.php?account_id=2891579&login_id=2&code=47416a22970b31ced1ab7bc492a8443b&guest_login=1&project_id=5501483 (used on The Invincibles Tour website.  Can be hidden or visible).

These are but a few of the many free and commercial Joomla components, modules and plugins that can be used to enhance the functionality of your website.  Click here for a comprehensive list of Joomla 1.5 extensions.