There are a number of ways to find modules to match the features you want to build:
- Use the search box at drupal.org and limit your search to modules.
- Visit the download & extend link at drupal.org to browse lists of popular modules. You can also go directly to http://drupal.org/project/Modules.
- Ask around in any of the available forums, to get the opinions of experienced Drupal developers about which modules match your requirements. You will find links to web forums and other ways of contact at http://drupal.org/getting-involved (including live chats). Wise people learn from others' experiences.
- Use your favorite search engine to search the internet.