I wasn't happy with the default highligting for assembly in Vim, so I wrote my own. This isn't perfect yet, but it's mostly usable. Feel free to contribute fixes and improvements.
Copy ca65.vim into your syntax folder (on windows it's
%UserProfile%/vimfiles/syntax/). It's installed now! \o/
In order for Vim to load up this syntax instead of the default, put the following line at the very top of your source files and leave the next line blank:
; asmsyntax=ca65
I've included a test file that lists all of the documented instructions as well as their addressing modes. Also included in this file are all instructions with improper addressing modes. These shouldn't highlight the same as correct addressing modes, but sometimes do (help me fix it).