There are so many different plug-ins, modules and components for Joomla it's not funny. A HUGE selection of them are on the main Joomla Extensions site but even more of them hide somewhere on the internet yet to be found and discovered.
Here is just a selection of my favourite Joomla add-ons that make my sites stand out a little more.
YOOeffects
This is a fantastic Web 2.0 style plugin. What does it do? Well, three few key features that really stand out al packed in to this little plugin.
YOOlightbox
This is similar to many of the lightboxes that you may find on the internet from the JQuery based lightboxes to the Prototype based ones. The difference with this lightbox is that it can easily lightbox, videos and even other sites. That is quite a step above other integrated lightbox solutions for Joomla. Very nice indeed.
YOOspotlight
Next is the spotlight feature, this is basically a glorified roll over effect but it is still VERY nice. It looks like an effect that you would have in a lot of flash sites. Used right it can be very effective.
YOOreflection
This is also a very nice effect that the YOO guys have put together. It is a common thing these days to see reflections in designs and Web 2.0 work. Seriously I was using reflections back in 2000 when I first started designing but still, thumbs up to the javascript approach to reflections.
You can download the entire YOOEffects plugin from their site.
YOOlogin
YOOLogin works on top of the regular Joomla login component. There aren't any additions to the functionality but the styling on the component is very nice. With fancy little graphics for "forgot password", "register" and login as well as some nice styling on the actual form fields. Another good download and addition for your Joomla site
Ultimate PNG Fix
This little plug in is essential for any work that you're doing that has transparent images. This fixes some of the issues that you will run in to when using transparent PNGs in your design and that pesky IE6.
It's quick and light and very easy to install and works natively with Joomla 1.5.x. You can download it from the JoomlaWorks website.
Tabs & Slides
These are fantastic addition to any site. Instead of having a huge page of content, why not divide it in to tabbed sections or even slide sections. These tabbs and slides are fully customisable via CSS and have cool animation effects thanks to the javascript implemented. It would be nice to see some fade effects placed in to it as well. You can download the plug in from the Joomla Works website and it works both in Joomla 1.0.x and Joomla 1.5.x.
Front Page Slide Show
Now this particular component isn't free, but is a fantastic was of show casing some of the featured stories or products on the front page of your site. You might have seen similar modules on the front page of Yahoo.com. This is fully customisable and very easy to configure. You plug in the images and information and away you go. It can randomly order your images or it can display them in a particular order. Unfortunately this one will cost you a little bit for the download but seriously is worth it when used in the right situations.
You'll need to go to the Joomla Works and register and pay for it before you can get access to it.
Conclusion
These are just a handful of extensions for Joomla. If you have any more or you're one of those little obscure ones, please post a comment and let us know.