- Introduction to X86-64 Assembly for Compiler Writers
- I highly recommend this guide. Fairly comprehensive, concrete, and not too difficult.
- x86 Assembly Guide
- Good intro, but note that this covers the x86 (32-bit) ABI, not x86-64. Specifically, the registers have been expanded, and the calling convention has changed!
- Easy x86-64
- Easy tutorial, not very in-depth
- x86-64 Handout
- x86-64 Calling Convention
- Stack frame layout on x86-64