Read picture books online

http://www.wegivebooks.org/books#all

Holiday-themed paper art

http://www.thetoymaker.com/Holidays/Christmas/Christmas.html

This includes a snowman dodecahedron--very fun.

Preschool Science

Activities: http://www.peepandthebigwideworld.com/activities/activities-location.html

There are also videos, games, and printables.

e-Learning Links

Another homeschool resource aggregator.

http://www.e-learninglinks.com/index.htm

Join real online research projects

https://www.zooniverse.org/projects

History of Science (and Technology)

http://www.bbc.co.uk/archive/tomorrowsworld/index.shtml

History of Medicine

http://www.sciencemuseum.org.uk/broughttolife.aspx

Bar Graph Tool

http://www.ngfl-cymru.org.uk/vtc/2008-09/fp/irf08-81/colour_patterns/years_1_and_2/bar_graph.html

This allows you to name your graph as well as each axis, and then build a graph.

Another Homeschool Link Aggregator

http://www.myfreeonlineeducation.com/

Weather and Physics experiments

http://www.metlink.org/weather-climate-resources-teachers/experiments-and-demonstrations.html

Unit on Seeds

http://www.bbsrc.ac.uk/society/schools/keystage1-2/seeds-plant-growth.aspx

This is heavy on activities.

Fungi Unit

http://www.bbsrc.ac.uk/web/FILES/Resources/mushroom.pdf

This includes lessons, worksheets, and cool experiments (like dying wool with fungi).

Bugs Unit

Download the .pdfs: http://www.bbsrc.ac.uk/society/schools/keystage1-2/real-bugs.aspx

Great ideas!

Elementary Life Science Text

http://eequalsmcq.com/ClassicScienceLife.htm

Both the student and parent editions are available.

Open Courseware at UW

http://www.outreach.washington.edu/openuw/

Animal Diversity Web

http://animaldiversity.ummz.umich.edu/site/index.html

Butterfly Lab

Everything butterfly, including a field guide.

http://www.naturemuseum.org/online/thebutterflylab/index.htm

Or this one:
http://kidsbutterfly.org/

AWESOME lessons on science (mostly genetics)

This is a fantastic site. Entire lessons, completely online. Check out the "learning pathways" section.

http://www.nature.com/scitable

Insects--great insects site

http://www.insects.org/

Science Net Links

This is one of the best places to go for resources on science. I think I've posted their link before, but they recently re-designed their site, and all the materials are accessible now.

The "Tools" are my favorite--they are the best interactives from around the web.

http://sciencenetlinks.com/