Popular resources and study materials for UPSC preparation include a range of books, online platforms, and coaching institutes. Iconic texts like Ncert, Laxmikanth for Indian polity, and GC Leong for geography are highly recommended. Additionally, well-structured online courses, study groups, and current affairs magazines like Yojana and Kurukshetra can enhance understanding. Aspirants also utilize platforms like YouTube and various mobile applications for interactive learning. Ultimately, it's crucial for candidates to curate their resources according to individual strengths and weaknesses for effective preparation.