After having seen what little material there is for amigoids interested in assembler we decided to try to collect some bits and pieces we have found useful. This page is under heavy construction, and will be probably continue being that in the foreseeable future.
As with almost anything else, tools, and some documentation, needed for working with assembler can be found on Aminet. Two examples of assembler packages in these archives are Barfly and PhxAss (PhoenixAssembler). Yet another assembler is SNMA. Personally I use Devpac, a commercial solution from HiSoft, which I thouroughly recommend.
On ftp://x2ftp.oulo.fi/pub/amiga/prog/ there is some material. Many of the assembler oriented files can be characterized as more or less "demo oriented"(take a look if you don't understand what I mean).
There are some sources to look at. They may be of uneven quality, but you're not paying for this are you? ;) Information about processors is a must, so why not take a look at MC680x0.guide by Flint/Darkness, converted to HTML with AG2HTML.
If you have any suggestions, please mail to one, or both, of the addresses below.