- Mathworld's topology page: http://mathworld.wolfram.com/Topology.html
- An intro to topology video: https://www.youtube.com/watch?v=C-eJW0gEm5w
- An online textbook from Sydney Morris: http://www.topologywithouttears.net/topbook.pdf
- Topology and geometry games from Jeff Weeks: http://www.geometrygames.org