Armasm is a project mainly written in Vim Script, it's free.
Syntax highlighting for ARM assembler
This is a mirror of http://www.vim.org/scripts/script.php?script_id=888
Syntax highlighting for ARM assembly language. It includes V2, V3, V4, V5, T, E, M, XS, and VFP extensions, but no V6 or T2 syntax. It is based on Aleksandar Veselinovic's PIC16F84 Assembler syntax file (pic.vim in the standard installation).