Autson Skitter Slideshow for joomla with tons of effects. You just add the images in the module backend then you go. Never been easier than this.

BT Slideshow is a perfect slideshow module for Joomla. It allows you to easily display images with many flash type animations done in Javascript.

Core Design Login module for Joomla! 1.5 and Joomla 1.7 based on Highslide JS. This module displays a Username and Password login form. It also displays a link to retrieve a forgotten password. If user registration is enabled

yvComment is native Joomla! 1.6, 1.7 (and Joomla! 1.5) Commenting solution, it is well documented and free.
It has two required parts (i.e., extensions): component + plugin.

jDownloads is a extensive Download Manager for the award winning Content Management System (CMS) Joomla. It is a free GPL Extension with many special functions!

Art Sexy Lightbox Lite Edition – Free Joomla! popup for local images. It contains the basic functionality of extremely popular Art Sexy Lightbox extension.

Fanbox also known as Likebox is a Joomla Module that displays Facebook Fan box/Like box into Joomla 1.5 ,1.6,1.7 websites.

The DJ-Image Slider extension allows you to display image slides with title and short description linked to any menu item or url address.