I'll keep dropping more and more stuff here as I come across it.

Mathematics

Algebra / Statistics

• Linear Algebra Stanford
• Convex Optimization Part I and Part II
• No frills matrix cookbook
• Stats and probability cheatsheet

Machine Learning

Courses

• Coursera- ML Andrew NG
• Statistical Learning Stanford
• Learning From Data- CalTech/edX

Deep Learning

• Most cited papers
• Ultimate DL book
• DL review- Nature
• Microsoft ML cheat sheet
• CS229 handouts

Digital Signal Processing

• EPFL course
• DSP Formula Sheet