I was doing some more surfing, as a result of all my reading (trade magazines) and came across various links that may be of interest here:
First:
The Society for Amateur Scientists
http://www.sas.org
Then, some free/open source software (graphing, modeling, data analysis,...)
http://www.opendx.org/
http://www.xfig.org/
http://www.fftw.org/
http://sources.redhat.com/gsl/
http://www.cadsoftusa.com/
Enjoy.