Backports.org has released a backport of MySQL 4.0.18 for Debian GNU/Linux 3.0

MySQL is a fast, stable and true multi-user, multi-threaded SQL database server. SQL (Structured Query Language) is the most popular database query language in the world. The main goals of MySQL are speed, robustness and ease to use.

Here the APT source:

# MySQL
deb http://www.backports.org/debian stable mysql-dfsg
deb-src http://www.backports.org/debian stable mysql-dfsg