Here's one that seems decent that I ran across with a simple google search. I starts off with programs that mix C and ASM, but that's actually a good place to start since getting basic ASM code working is much easier if you piggyback on the excecution setup a compiled C program provides. If you don't already know C, I really do suggest you try to learn it first because it will familiarise you with many programming concepts that will make writing good assembler code much easier. Anyway, give it a shot and see if it suits your needs.