Writing forms: http://www.netrover.com/~kingskid/letter/forms.html
Letter Generator: http://www.readwritethink.org/files/resources/interactives/letter_generator/
Writing Detective: http://www.harcourtschool.com/activity/trophies/writing_detective/WD_E_2_2.HTM
Letters to Arthur: http://pbskids.org/arthur/games/letterstoarthur/
Writing Letters: http://www.joelson.addr.com/letterwriting.htm
Writing Den: http://www2.actden.com/Writ_Den/