Science oriented LiveCD
Blue Obelisk Live CD by Egon Willighagen
GNOME Science CD (early state)
Other science distributions
Bio-Linux Standard and cutting edge ?BioInformatics software tools on (as of version 4.0) a Debian GNU/Linux base.
In Ubuntu: Ubuntu Science, and MOTU Science Team.
Comparison of Ubuntu and Debian science package versions http://qa.ubuntuwire.com/multidistrotools/science.html
Scubuntu aims to produce an ubuntu based distribution for scientists - and has a list of scientific software: http://scubuntu.meraka.org.za/wiki/Scientific_Software
Scibuntu another ubuntu based science distribution.
Unofficial Debian repositories with science software
DanielLeidert repository (read this)
Yorick repository; etch-backports, unstable; i386, ppc, amd64
CERN High energy physics /CERN related.
Bio-Linux WARNING Read This Warning
Other free software project sites
Some tutorials and examples (link provided by Andre Lehovich)
From IDL to Python (link provided by JD Rogers)
DebianScience/Geant4 a toolkit for the simulation of the passage of particles through matter. (unofficial packages exist)
Scientific software lists
http://www.opennovation.org/ Categorised list of software useful for engineering.
http://heybryan.org/mediawiki/index.php/Comp_chem_linkdump Computational chemistry software - some of it free.
Mailing lists devoted to open source scientific software
http://lists.okfn.org/cgi-bin/mailman/listinfo/open-science Mailing list devoted to open source science.