E.T.
I've heard that Target will be ending their program, but I don't know if it is true. Too bad if they do. Our local schools earned over $11,000 last year.
You can collect Cambells soup labels (on lots of other products as well). Coke bottle caps have codes inside that can be redeemed for points. We have a local convenience store (Kwik Trip) give 5 cents per bottle cap from their store brand milk. I think their pizza boxes also have a redeemable label for schools. Those are the things our school does on an ongoing basis.
One time events:
Restaurants that donate a portion of their sales for one night. (Wendy's, Chipotle, Brueggers Bagels, a locally owned pizza place)
Barnes and Noble book fairs
We have a local toy store/teacher supply store that also will host fundraisers with a portion of sales from a weekend going to a school.
Our state has a Give to the Max day that schools can register for as well.