How to Find Drupal Modules
Drupal's core is a solid framework in which users with no programming experience can build a website, but there are some features you may need that Drupal core does not support. Before you consider custom development, try looking for a contributed Drupal module. Contributed modules allow functionality for extended features such as having a Twitter feed on your website or allowing users to create friendships and message each other. So how do you find these modules? The majority of Drupal modules for download are located at http://drupal.org/project/Modules and below is some information on how to navigate this section on the Drupal.org site.
Several different filters are located on the right side of the Drupal.org Modules page. If you know the name of the module or keyword you are looking for, you can search for it under the "Search modules" section. If you would rather browse modules to see what is available, the filter you will want to choose first is your Drupal version under the "Filter by compatibility" section. Filtering a version displays modules available for download for the version you select. If you downloaded Drupal or LevelTen iSite Essentials in the last 6 months or so, you will want to select "6.x" as your Drupal version.
After you filter by your Drupal version, there are several categories in which to browse modules. These are located in the "Projects" section on the right side of the Modules page. If I were looking for a video player module for Drupal, I might click on the "Media" category. By default, the modules are sorted alphabetically, and you will need to browse page by page to view the available modules.
There are a two sorting options I would recommend in order to help you find a good module within your chosen category. On the right side you will see the "Sort by" section. Usually, you will want a module that is consistently being updated with bug fixes and/or new features. A start for looking for these modules is to filter by "Last release." This will sort the results to bring up the most recent releases. You can then click on a module title to view the module's information page. A good judge for a module that has been updated consistently is to view the releases history by clicking on the "View all releases" link. This will give you a history of updates and a gauge for how often the module may be updated in the future. Going back to the "Sort by" section on the Modules page. The other "Sort by" option that is useful is "Usage statistics." Modules reported as being used the most will display first. Popular modules usually have a good community backing and consistent updates.
Hopefully this gives you a good start for finding contributed Drupal modules that help extend functionality on your site. Other good information on contributed modules, including installation instructions, can be found at http://drupal.org/node/340271. Try experimenting with different modules and settings in those modules. The fun is finding one that hits the spot for your needs and avoiding the cost of custom development.