What is a good summer job for an Elementary Education major?

A camp is a great place to work if it is an educational camp like Space Camp or the like. "Traditional camps" give you exposer to children which is great experience, but may not offer you a whole lot of intellectual interaction.
Also consider a learning center or a library.
I worked for a year round school during the summer, so you can try looking at summer classes there.

Child care, parks and recreation, scouting or other kids summer camps, etc. Any place where you will have to interact with kids of the ages you intend to teach. The experience will be invaluable. Good luck.
A day care facility.
Camp counselor.

Good resume builder and fun.

(pay sucks though).