IEAR (I Education Apps Review) — This is the first place I look to find apps that have been reviewed by educators. You can use the links on the left side to narrow your search.
Learning in Hand – Tony Vincent has some great tips, tricks, and links for using ipod touches. Be sure to explore the rest of the site.
Learning Continuity – You can sort apps by discipline and cost here.
iNtouch School — Great resource about using ipod touches in the classroom. Be sure to explore the rest of the site.
AppShopper – (make sure to use the search features on this site to help narrow your search)
Speech-Language Pathology Sharing – Eric Sailers often writes about ipodtouch apps and how they can be used in special education. Really, though, many of the things he writes about can be used across all levels.