I have used the resources below and found them useful, especially for beginners. Any suggestions or additions to this list are most welcome!
 N-body simulations of gravitational dynamics, W. Dehnen and J.I. Read (Paper).
Gravitational N-body Simulations, Michele Trenti and Piet Hut (Paper).
Introduction to Gravitational Lensing, Massimo Meneghetti (Notes).
Lectures on Gravitational Lensing, Ramesh Narayan & Matthias Bartelmann (Notes).
Gravitational Lensing, a lecture by Professor Jasjeet Bagla (Video).
Astronomical data analysis using Python, Yogesh Wadedar (Video Playlist).
Physics Problems in Python, Mr P Solver (Video Playlist).
Python for Astronomy and Astrophysics, Desi Astro (Video Playlist).
Introductory Python, Rajat Saxena and Gauri Padalkar, LI-EPO
Fundamentals of Statistical and Thermal Physics, Frederick Reif (Textbook).
Entropy, Order Parameters, and Complexity, James Sethna (Textbook with Project Problems).
Notes on Statistical Mechanics, K.P.N. Murthy (Notes).
Detection of radio emission from pulsars: A pulsar observation primer, Dipankar Bhattacharya (Notes).
Radio Astronomy Winter School (RAWS), IUCAA-NCRA (Video Playlist).
Essential Radio Astronomy, James J. Condon and Scott M. Ransom (Textbook).
Astro Tutorial #1: Theory, Catching Photons (Video Playlist).
A-Z Constellations, Learn the Sky, (Video Playlist).
Celestial Objects, Learn the Sky, (Video Playlist).