These organizations have some great resources on their web sites, including a lot of lesson plans! Click on the logo of a source to go to that web page.
Of course, I HAVE TO list my all time FAVORITE teacher organization first! OKAGE taught me to teach geography! I went to my first teacher training with them fifteen years ago, and it changed the way I understood teaching geography! Their site has many lesson plans free for your use. (You have to register, but it's free.)