National Childhood Brain Tumor Prevention Network Act of 2008 - Amends the Public Health Service Act to require the Director of the National Institutes of Health (NIH), acting through the Director of the National Cancer Institute, to establish, administer, and coordinate a National Childhood Brain Tumor Prevention Network to: (1) provide grants for research on the causes of and risk factors associated with childhood brain tumors; (2) assemble a panel of experts to provide ongoing guidance and recommendations on research funded by the Network, including on a common study design and standard protocols; and (3) designate a central laboratory to collect, analyze, and aggregate data with respect to research funded by the Network and to make such data and analysis available to researchers.