If you find you need additional Apt repositories in the configuration file, try the following online locations:
As well as being a primary site for the download of Apt, additional repositories and documentation exist here, too.
The original RPM-based Apt site on SourceForge is a great source for all kinds of things, including repositories for Red Hat SuSE, Mandrake and Yellow Dog.
Very helpful for desktop Linux users. This site is specific to Red Hat and KDE.
A great source for Apt repositories and many other things Linux.
Fedora will continue to support Apt but will also support an additional configuration-managed utility called Yum. For more information, go to the Red Hat site.