Science Forums
Many topics covered; for beginners to serious researchers.
http://www.scienceforums.net/

Able2Know - Science & Mathematics
Make inquiries about science and math topics, as well participate in discussions and debates.
http://www.able2know.com/forums/ask-about71.html

Element Science Community Forums
A place to post about any science-related topic.
http://www.elementlist.com/lnx/index.php?action=displaycat&catid=29

Lab-monkeys.com
A community of students, technicians, post-doctorates, and researchers to have discussions of science, lab-life, careers, and education.
http://www.lab-monkeys.com/forums/

Plastictalk Forum
A plastics discussion forum for the plastics and rubber industry worldwide.
http://www.plastictalk.com/forum/

The Science Forum
Discussion topics include astronomy, cosmology, biology, chemistry, earth sciences, physics, social sciences, health, medicine, history, economics, business, engineering, computer science, math and environmental issues.
http://www.thescienceforum.com/

Science Chat Forum
An advanced discussion forum for science, philosophy, and related matters. Multiple forums, career announcements, and a dynamic IRC chatroom.
http://www.sciencechatforum.com/

Science Forum: Philosophy Physics Metaphysics of Space
Science discussion of physical reality, Space and Matter.
http://www.physics-philosophy-metaphysics.com/forum/index.php

Sci-Tech.co.uk
A place to learn and discuss various aspects of science and technology and how they interact.
http://www.sci-tech.co.uk/

The Science Advisory Board
A global community of life scientists who convene to share knowledge and comment on emerging technologies.
http://www.scienceboard.net/forum/

PhysicsMathForums.com
Features discussions in the areas of physics, astronomy, math and philosophy.
http://physicsmathforums.com/

Scientist Solutions
Features discussion board topics for analytical chemistry, anatomy, physiology, biotechnology, biochemistry, bioethics, bioinformatics, biophysics, cell biology, cell transduction, molecular pathology, genetics, genomics, immunology, microbiology, neuroscience, and pharmacology.
http://www.scientistsolutions.com

Duckalogue
Offers discussion about sports, book reviews, scientific studies, and commentaries on modern concerns.
http://duckalogue.blogspot.com/

InsectHobbyist
An independent online community of Insect and Arachnid hobbyists, businesses, keepers, breeders, and organizations. Chat rooms, WebRadio, classifieds, feature pages, and lots of forums. Part of the PetHobbyist community.
http://www.insecthobbyist.com/