Check out MarcoPolo, a website full of lesson plans and weblinks on tons of subjects. MarcoPolo was recently voted the top site for free educational resources online by Wisconsin teachers.
"MarcoPolo is a partnership among leading educational organizations and the Verizon foundation. MarcoPolo is a gateway to seven discipline-specific sites, with resources furnished by the
* John F. Kennedy Center for the Performing Arts,
* National Council on Economic Education,
* National Endowment for the Humanities,
* National Council of Teachers of Mathematics,
* International Reading Association,
* National Council of Teachers of English,
* American Association for the Advancement of Science and
* National Geographic Society."