OnLine Research Modules- This is a great model. The site is from Australia, so many of the topics don't work for us, but the format is ideal.
All Men are Created Equal? a web quest
Social Studies web quests grades 3-5
Winter Celebrations - a web quest for second grade
Native American Research Module
Curriculum Based Research Modules - another model site created by teachers at Loyola College Graduate Program
Teacher Tips and Tools - this one comes from Maryland