The purpose of this study is to determine the feasibility and efficacy of a behavioral intervention, delivered through an existing social networking website (Facebook), on physical activity (moderate-intensity minutes per week) among young adult cancer survivors compared to a self-help education condition. For this research study, investigators will conduct a 12-week randomized trial. After a baseline survey, weekly messages, a pedometer, goal-setting tool, physical activity log and discussion prompts will be delivered to the intervention group. Comparison group participants will receive links to websites with self-help education materials. After 12 weeks, a follow-up survey will be given to both groups. Changes in physical activity, quality of life and psychosocial factors will be examined. The investigators hypothesize that those receiving the intervention will have improved physical activity behaviors at 12-week follow-up relative to those in the comparison group.