Debian Sarge release notes

Debian sarge release notes
Upgrade issues
key point:
You are therefore strongly advised NOT to upgrade to a 2.6 kernel as part of the upgrade from woody to sarge. Instead, you should first make sure your system works correctly with either the old kernel or with a 2.4 kernel from sarge and do the upgrade to a 2.6 kernel later as a separate project.

other useful stuff:
Debian sources wikipage