At Sanaga-Yong, near the small city of Bélabo, the US based NGO, In Defense of Animals, operates a shelter for chimpanzees that have been rescued from poachers or from being kept illegally. It's an impressive facility, where the chimps, although caged, are kept in very large fenced enclosures with a very natural environment that gives them room to roam. Visiting the facility provides a chance to not only see the good work that IDA is doing, but see the chimps in something like a natural habitat. The facility contains an educational center that visitors can peruse, and tours are available at specific times, which are unfortunately not listed on the organization's web site, but could probably be obtained by e-mail from the home office in the US.
The only difficulty with visiting the Center is reaching it. Transportation to Bélabo is available by a good paved road or by train, but unless you have your own vehicle, you would need to hire a taxi for the 30-40 minute drive to the site, as I was told that bush taxis pass only intermittently.