Linux can be used as a mean to protect our environment, by using its features to save power or paper, since it doesn't require big hardware it may be used with old computers to make their life cycle longer, games may be used in environmental education and software is available to simulate ecological processes. To follow this way I set up a page about Linux and Ecology. You may find my Linux-Ecology-HOWTO and a mailing list there.
Working as a system administrator in the computer departments of two German hospitals I get inspired to search for medical applications created with Linux software. So I have collected a survey of Linux software for the medical sciences in the Medicine-HOWTO.