Free online resources for UPSC exam preparation include platforms like Unacademy, which offers free classes, and websites like Insights on India and Clear IAS for study materials and strategies. Additionally, YouTube channels provide valuable tutorials on various subjects, while government portals like Press Information Bureau keep candidates updated on current affairs. Discussion forums on platforms like Reddit and Telegram groups also allow for sharing resources and tips among aspirants. Utilizing these resources can significantly enhance preparation without incurring additional costs.