As an alternative for learning, I'd suggest using an emulator and programming for some sane instruction set. Maybe the MC6809 which had a nice, clean, easily comprehensible instruction set. (I'm sure that there are other equally good choices). If one still has an interest in assembly language programming after that, then by all means tackle x86. You'll probably be appalled.
*sigh*
I just shed a tear, I had forgotten the beauty of coding 6809 assembler back in the old
CoCo/Dragon32 days. From personal experience, it is indeed a great platform to learn a decent/simple assembler.
(on a side note, wasn't the 6809 the only one of the then popular processors to implement integer multiplication in hardware? ah! the beauty of "MUL")
If interested, I would recommend downloading either Paul Burgin's "T3" Dragon32/CoCo emulator for the PC or Xroar, (first hit for "Xroar" in google, multi platform) and have a go at it. Of course it requires a "fast machine" (something like a 386DX 33 will be enough for T3 ;o) and the original Dragon ROMs. (getting hold of the ALLDREAM Editor/Assembler would also be a great bonus if you are pursuing this route)
(please, insert mandatory reference to "people getting off my lawn" at your discretion)