This directory, dists, is the canonical way to access the distributions.
Each distribution can be accessed by name or state from here.

stable, or lenny    - the released Debian 5.0.6.
proposed-updates    - possible updates to Debian 5.0.  See the README there.
testing, or squeeze - the development version of the next release.
unstable, or sid    - untested candidate packages for future releases.