68000:
I found this rather helpful when reversing 68000 CPU games. It's great for referencing what instructions set what flags or are checked against flags and basically looking up an instruction you're not sure of:
http://www.cs.tcu.edu/people/professors ... _Instr.pdf
Z80:
Instruction Set: http://www.phy.davidson.edu/fachome/dmb ... %20set.pdf
6502:
An excellent reference for 6502 instructions:
http://www.obelisk.demon.co.uk/6502/instructions.html
65C816:
Everything you'd ever need to know about the 65C816 (Also contains info for 6502, 65C02, and 65802)
The (extremely detailed) instruction set start on page 326
http://www.westerndesigncenter.com/wdc/ ... manual.pdf
Arm 7 Thumb:
Instruction set: http://infocenter.arm.com/help/topic/co ... 01_UAL.pdf
I'd put more but I'm only allowed 5 URL's
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