This site has searchable video cases of real elementary math lessons teaching standards based mathematics lessons. You can also see a complete lesson plan with handouts.
The NCTM website has excellent ideas for lesson plans, interactive on-line math activities, challenge problems, and more. NCTM offers many professional development resources such as journals, on-line conferences, information about regional conferences, an
Great resouce for children's literature applicable to math lessons. You can search by grade or topic. The site also has links to some lesson plans and online activities which go with some of the books.