So, what's the best method to run this on a Mac if it's not natively supported? A Windows XP Virtual Machine / Boot Camp / MacPort / any suggestions?

Thanks.

BootCamp, if you can and can be bothered to dual-boot. Other than that, virtual machines (http://worms2d.info/Emulating_Worms_Armageddon).

Unfortunately WA isn't Mac compatible - it was being ported to Mac by another company ages ago but that project got cancelled during a takeover.

The best option will be to use Boot Camp to run the game in XP, as there is no virtualisation involved which will potentially slow the game down. However this does mean that you'll have to reboot your computer into Windows each time you want to play. Although given that WA is a 10 year old game, modern virtualisation software such as VMWare Fusion and Parallels should be able to make a half-decent attempt at playing it. Note that if you still have an old PowerPC Mac, the only option will be to use Virtual PC - which is awful and slow and can't really manage WA!