My friend is looking for organizations that will donate books for poor
high schoolers in Guyana:

"I'm just looking for things normal high school kids would find
interesting........anything under that genre would be awesome.  They're just
hungry for knowledge, anything they can understand (niothing technical) they
would love.  One thing I am really looking for is charitable organizations
that do these things........since i only have limited internet access that
makes this hard.  Help finding these would be great.  So far I can only find
bookaid@aol."

What other organizations are there that might be able to help him out?

Check out the following organizations:

Books for the World
Brothers Brother
International Book Bank
World Vision

I'm not sure who's active in Guyana.  There's another cool group that
focuses on Africa -- Books for Africa.  I mention them because they
seem pretty knowledgable about the book donation/shipping business and
may know other orgs. that might be active in Latin America.  Good
luck!