AmblesideOnline's Nature Study schedules and info
Fantastic site in general and home of the Outdoor Hour (helps on how to do nature study):
http://handbookofnaturestudy.blogspot.com/
Awesome for nature journaling:
http://www.creatingnaturejournals.com/
Coloring pages of birds and insects
http://thecoloringspot.com/birds/index.html
E-mail support group (not currently very active)
http://groups.yahoo.com/group/UsingHONS
Full text of Anna Botsford Comstock's Handbook of Nature Study
same book on Google books
For my Texan friends: Outdoor Kids printable journal
If you know of other great links, please post them in the comments!
Amy