Here are two resources I was able to find:

This one looks very promising. The organization is Book Aid International and they work with a variety of programs on a local level. Depending on where you are specifically located, they list three possible options (these options are listed on this site: http://www.bookaid.org/cms.cgi/site/our_work/contacts/_tanzania.htm)

Option 1: If operating in mainland Tanzania, a request should be directed to Tanzania Library Services Board (http://www.tlsb.or.tz/) by email (tlsb@africaonline.co.tz)