Books

• Competitive Programming 3 by Steven Halim and Felix Halim
• Competitive Programmer's Handbook by Antti Laaksonen ²
• Principles of Algorithmic Problem Solving by Johan Sannemo (in progress)

Math/geometry-oriented

• Trophy Hunting in the Infinite Jungle of Finitude by Janne Junnila
• Handbook of geometry for competitive programmers by Victor Lecomte (in progress) ³

Blogs

• The bit talk
• Threads @ IIIT Hyderabad

Math-oriented

• COME ON CODE ON
• I write, therefore I am

Collections

• Awesome Competitive Programming