Here are the URLs for some web sites that have information pertinent to teaching mathematics for grades K-8. All of these sites provide links to additional mathematical sites pertaining to K-8 education.
The home page for the Math Forum at Swarthmore.
http://www.nctm.org/standards2000/
Information about the NCTM draft publication of Principles and Standards for School Mathematics.
http://forum.swarthmore.edu/geopow/
Gives the geometry problem of the week posted by the Math Forum at Swarthmore.
http://forum.swarthmore.edu/~steve/steve/mathgeom.html
The geometry page for the Math Forum.
http://www.stolaf.edu/stolaf/other/extend/
EXTEND: Perspectives on Mathematics Education.
EXTEND is a national Internet forum on mathematics education intended to involve new constituencies, to engage new voices, and to examine new perspectives. Major topics will be explored through forum reports, position papers, and reader commentary. These topics are addressed from many perspectives, including those of educators and employers, business leaders and public officials. In addition, EXTEND provides information on innovative programs and links to important documents related to reform of mathematics education in schools, colleges, and universities.
http://math.rice.edu/~lanius/Geom/index.html
Includes several geometry activities, a brief history of geometry, and a limited glossary of geometric terms. (For some reason it seems to load quite slowly on my computer.)
http://www.dpi.state.wi.us/dpi/standards/matintro.html
A summary document for the new Model Academic Standards in Mathematics for Wisconsin. Links are provided to the standards in each of the areas of mathematics, including geometry.