As this develops further, links may be categorized and/or flagged for type and level of content. Please suggest whatever paid or free resources you have found worthwhile, or even possibly worth a further look.

Books:

Curricula:

Building Foundations of Scientific Understanding (BFSU)

Tools:

Websites:

http://www.bbc.co.uk/schools/ks2bitesize/science/
http://www.bbc.co.uk/sn/
http://www.beestar.org
http://bodybrowser.googlelabs.com
http://curriculum.qcda.gov.uk/
http://enature.com
http://www.explorelearning.com $
http://www.hhmi.org/coolscience/ (Howard Hughes Medical Institute Cool Science)
http://science.howstuffworks.com
http://www.hww.ca/index_e.asp
http://www.jason.org/public/whatis/start.aspx
http://www.khanacademy.org
http://www.kineticbooks.com/ $
http://learn.genetics.utah.edu/
http://learn.genetics.utah.edu/content/begin/cells/scale/
http://www.micro.magnet.fsu.edu/optics/tutorials/index.html
http://missrumphiuseffect.blogspot.com/p/thematic-book-lists.htmlhttp://www.mlahanas.de/Greeks/Greeks.htm

http://www.neok12.com
http://www5.pbrc.hawaii.edu/microangela/index.html
http://www.pbskids.org/zoom/activities/sci/
http://www.periodictable.com/
http://www.periodicvideos.com/nyt/index.htm#
http://www.sheppardsoftware.com/science.htm
http://www.stellarium.org/
http://www.superchargedscience.com $
http://www.tolweb.org/tree/phylogeny.html
http://www.tryengineering.org/lesson.php?from=8&to=&cat_id=&keyword=
http://faculty.usiouxfalls.edu/arpeterson/science%20standards.htm
http://www.virlab.virginia.edu/VL/home.htm/state/0 (University of Virginia Virtual Lab)
http://www.visiblebody.com $
http://www.wikipedia.org
http://www.zooniverse.org/home