The clock is running for some Debian users. Security support for Debian GNU/Linux 3.0, alias "woody," is scheduled to be cut off at the end of the month. On June 30, the Debian project will turn off support for the four-year-old operating system. Details, here.
In a nutshell, security updates for this release will be distributed via security.debian.org until the end of June. Older updates will remain available on security.debian.org until December 2006.
The current version is Debian GNU/Linux 3.1, alias "sarge." It has been out since early June 2005. Debian generally provides users with a one-year time frame to upgrade their old installations to the current stable release.