i dont find the intel manuals to be any harder, and all those charts and tables that sandpile uses, are extracted from the intel manuals (and easily found by searching the intel PDF)
Maybe it's a bit difficult to read at first, but I prefer this to the Intel Manuals. There are some basics, for example "modRM-Byte", you need to know, but if you understand the principe it's very easy to look up the binary code for an instruction.
the opcode tables are ripped straight from the intel manuals, vol 2(b) appendix A.3 table A-2, A-3, A-4, and A-5 (currently blank) with the group tables in A4.2 table A-6 with escape ops in section A.5
a better map is the instruction encodings (not sure if its on sandpile -- though it probably is, im just dont use that site enough to know where) is appendix B -- table B-13 contains every general purpose non-64bit instruction in alphabetical order, and the binary encodings for it (its in section B.2, and on page B-9 in revision 19US), with other sections for other catagories (64bit, FPU, SSE, etc)
plus, each instruction gets its own section in the intel manuals, explaining in detail how it works, and how to use it, and how to encode it
in the end, its up to you which you use, but either way you should order the intel manuals,
and download the PDFs -- which are kept more up-to-date (and are searchable)
I can generate Assembler code, and using NAMS to building binaries, but I really want to learn building binaries myself 
