I've been out of touch for a while, and it took me way too long to set this up; but hey - better late than never. :-)
After looking into various options for the VexFlow mailing list, I eventually decided to use Google Groups. It's super easy to setup and manage, and has all the features I'll ever need.
If you're interested in hacking, discussing, or simply keeping up with VexFlow, sign up here:
Unfortunately, I haven't had the time lately to hack on VexFlow, but I assure you that it's only temporary. I have a bunch of partial changes in the works, along with some interesting ideas floating around. More later.