Debian 'new' queue

Debian has three available versions : a stable one, which is released about every two years, a testing one, which serves as a playground for testing new stable releases, and a development version, which changes every day.
People who run the "unstable" version receive every day (or every time they choose for it) new software versions. A good place to track new versions is the Debian 'new' queue, which shows packages in the pipe before entering unstable.