Debian is a free operating system distributed in three branches - stable, testing, and unstable. The distribution contains huge number of DEB packages (over 8700), which are well-tested stable pieces of free software.
It's not primarily intended for unexperienced users, as it doesn't contain any high-level software for system administration. The distribution consists of 1 to 7 CDs,
and may be instaled and updated (even upgraded) over LAN or internet.
Package versions are here: